Hello mvw and welcome to the forum!
(All emphasis by me.)
If salvation depended on us praying to receive Christ, why is it that no one in the Bible was ever saved as a result of praying to receive Christ?
Take for example, Paul prayed and fasted for three days prior to going to see Ananias, but his sins were not washed away at that time. No, Jesus specifically told Paul what he had to do... go and find Ananias and Ananias would tell Paul what he had to do. When Paul did find Ananias... what did Ananias tell Paul to do... did he tell him to pray to receive Christ? Nope! Here is what Ananias told Paul:
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
You see... "It's there in black and white."

In order to have his sins washed away... Paul was not instructed to pray to receive Christ, he was instructed to be baptized. Notice what Ananias stated Paul was doing... "calling on the name of the Lord." As the evidence shows, calling on the name of the Lord includes baptism to have our sins washed away.
Another example we have of someone praying in the Bible is of Cornelius... the centurion. I refer you to Acts chapter 10. Yes... Cornelius prayed daily... but he did not pray to receive Christ into his heart or into his life. Read the story and chapters following for the recaps and notice that in order for Cornelius and his family to be saved, they had to hear the word of God from Peter... ("the words by which you and your family will be saved") and they were baptized. Very interesting story.
Peter also teaches us all how we are to call on the name of the Lord. Recall the day of Pentecost? Luke recounts the story of Jesus commanding the apostles to go to Jerusalem and preach repentance and remission of sins...
Luke 24:46-47 And said unto them, Thus it is written, and thus it behoved Christ to suffer, and to rise from the dead the third day: And that
repentance and remission of sins should be preached in his name among all nations, beginning at Jerusalem.
They obeyed. Beginning in Jerusalem on the day of Pentecost we read that Peter preached...
Acts 2:16-21 But this is that which was spoken by the prophet Joel; And it shall come to pass in the last days, saith God, I will pour out of my Spirit upon all flesh: and your sons and your daughters shall prophesy, and your young men shall see visions, and your old men shall dream dreams: And on my servants and on my handmaidens I will pour out in those days of my Spirit; and they shall prophesy: And I will shew wonders in heaven above, and signs in the earth beneath; blood, and fire, and vapour of smoke: The sun shall be turned into darkness, and the moon into blood, before that great and notable day of the Lord come: And it shall come to pass,
that whosoever shall call on the name of the Lord shall be saved.
Let's answer two questions:
1. How did Peter preach repentance and remission of sins?
2. How did Peter tell these people to call on the name of the Lord?
For the answers, we simply go to the Scriptures following:
First, Peter preached the gospel to the people...
Acts 2:22-36 Ye men of Israel, hear these words; Jesus of Nazareth, a man approved of God among you by miracles and wonders and signs, which God did by him in the midst of you, as ye yourselves also know: Him, being delivered by the determinate counsel and foreknowledge of God, ye have taken, and by wicked hands have crucified and slain: Whom God hath raised up, having loosed the pains of death: because it was not possible that he should be holden of it. For David speaketh concerning him, I foresaw the Lord always before my face, for he is on my right hand, that I should not be moved: Therefore did my heart rejoice, and my tongue was glad; moreover also my flesh shall rest in hope: Because thou wilt not leave my soul in hell, neither wilt thou suffer thine Holy One to see corruption. Thou hast made known to me the ways of life; thou shalt make me full of joy with thy countenance. Men and brethren, let me freely speak unto you of the patriarch David, that he is both dead and buried, and his sepulchre is with us unto this day. Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne; He seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. This Jesus hath God raised up, whereof we all are witnesses. Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear. For David is not ascended into the heavens: but he saith himself, The LORD said unto my Lord, Sit thou on my right hand, Until I make thy foes thy footstool. Therefore let all the house of Israel know assuredly, that God hath made that same Jesus, whom ye have crucified, both Lord and Christ.
The people heard the message and were pricked to the heart... they wanted to know what they had to do to call on the name of the Lord...
Acts 2:37 Now when they heard this, they were pricked in their heart, and said unto Peter and to the rest of the apostles, Men and brethren, what shall we do?
Peter preaches repentance and remission of sins just like Jesus commanded and tells them exactly how to call on the name of the Lord...
Acts 2:38 Then Peter said unto them,
Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost.
You see... calling on the name of the Lord is not referring to praying to receive Christ... it is referring to obeying what God has commanded in order to be saved. This is how we call on God.
We must be baptized for what? For the remission of sins!
Jesus said to do what? Preach "repentance and remission of sins". What did Peter preach? "Repent, and be baptized... for the remission of sins..." Peter obeyed Jesus. Notice how the sins are forgiven, via baptism... not prayer. Peter did not tell them to pray to receive Christ... NOPE! Crystal clear!
The story you refer to about the snake on a poll is indeed a good example of the fact that we must obey what God tells us to do in order to have life. Of course this particular instance with Moses was only for those who had been snake bitten.
Numbers 21:9 And Moses made a serpent of brass, and put it upon a pole, and it came to pass, that if a serpent had bitten any man, when he beheld the serpent of brass, he lived.
Similarly God tells those who are lost (snake bitten and dying so to speak) that they must be baptized to live, therefore we must be baptized. No one here is claiming the water has any special power, nor does the Bible claim it has any special power, but we are commanded to be baptized to have our sins washed away. Baptism is how we come in contact with the blood of Christ. We are buried with Him...
Colossians 2:12 Buried with him in baptism, wherein also ye are risen with him through the faith of the operation of God, who hath raised him from the dead.
Romans 6:3-5 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life. For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
As you so very well state... God does command us to obey Him... He commands us to be baptized for the remission of our sins,
but no where does He command us to pray to be received.
Now you gave us one passage and misinterpreted its true meaning in order to support a man-made doctrine of prayer for salvation, which we have clearly shown and proven with multiple Scriptures is absolutely false teaching.
Next you claim baptism is something we do after we are saved, but you fail to offer any supporting Scripture for your claim. I suspect that is because it is not taught any where in the Bible.
Then you state that baptism is a meaningless act without first accepting Christ, but you offer no Scriptural support for your claim. Furthermore the Bible clearly disagrees with your claim.
Surely you see
the truth now. I feel confident that you believe and have faith... understanding that Jesus died on the cross for our sins.
1 Corinthians 15:1-4 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand; By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain. For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures; And that he was buried, and that he rose again the third day according to the scriptures:
Most likely you have repented for most of your sinful ways. Now you should repent of worshiping in vain and turn to the truth... worshiping in spirit and in truth...
John 4:23-24 But the hour cometh, and now is, when the true worshippers shall worship the Father in spirit and in truth: for the Father seeketh such to worship him. God is a Spirit: and they that worship him must worship him in spirit and in truth.
We must repent or Jesus explained we will surely perish...
Luke 13:3 I tell you, Nay: but, except ye repent, ye shall all likewise perish.
God also commands us to repent... not to pray to receive Christ, but to repent...
Acts 17:30 And the times of this ignorance God winked at; but now commandeth all men every where to repent:
Jesus says we must confess Him before other men...
Matthew 10:32 Whosoever therefore shall confess me before men, him will I confess also before my Father which is in heaven.
Therefore you should make sure you confess Jesus, just as the Ethiopian Eunuch did...
Acts 8:36-38 And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God. And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him.
Then right there in your Bible... possibly in black and white, but most likely in red and white... Jesus said,
Mark 16:16 He that believeth
and is baptized shall be saved; but he that believeth not shall be damned.
He that believes and is baptized will be saved! Amen!
So I ask you mvw... why do you delay? Arise and be baptized, washing away your sins, calling on the name of the Lord.
1 Peter 3:21 The like figure whereunto even
baptism doth also now save us (not the putting away of the filth of the flesh, but the answer of a good conscience toward God,) by the resurrection of Jesus Christ:
Now on to the thief on the cross... such a mis-used aid for false teachers who claim baptism is not necessary for salvation.
The thief was not commanded by Jesus to be baptized... it would have been impossible for the thief to obey the gospel because the gospel (the death, burial and resurrection of Christ) had not been consummated at the point that Jesus spoke to the thief on the cross. The thief lived under the old law... we live under the new law. Jesus had all authority to do as He pleased while He was on this earth... He could forgive sins on the spot and did in many instances, just as He did with the thief. Jesus gave the command of baptism after He rose from the grave... it is part of the new law... the new covenant. For a complete overview on the thief... see this article...
What About The Thief On The Cross?
Not only is praying to receive Christ a "man-made" doctrine...
It is nowhere found in the Bible...
No one ever prayed to receive Christ in the Bible...
Every example of salvation under the New Testament, the covenant under which we live, includes baptism...
Praying to receive Christ is a false teaching that Satan wants everyone to believe is true... and it is one of the major reasons Jesus said "many" will follow the broad path to destruction and "few" will find eternal life... (Matthew 7:13, 14)