The Lord said to Gideon, "The people with you are too many for me to give the Midianites into their hand, lest Israel boast over me, saying, 'My own hand has saved me.’”
The Lord said it in the Old Testament and demonstrated in a graphic way when he had Gideon defeat Midian’s vast army with only 300 men. The principle he taught is that the Lord saves and he is the only one who does. When we start thinking we are able to save ourselves in any way, then we would be able to boast to God about it. We don’t even have the ability to choose God unless he first causes us to be alive instead of dead in our transgressions (Eph 2:5).
Oh sing to the Lord a new song,
for he has done marvelous things!
His right hand and his holy arm
have worked salvation for him.
God repeats the fact that he alone saves when he tells us to praise him in song because of what he has done. We don’t praise the Lord for what we have done when we are saved. He reminds us that it is his holy arm that works salvation for us. “Jesus paid it all, all to him we owe” are the words to the song we sing about our salvation.
And he said, "Jesus, remember me when you come into your kingdom." And he said to him, "Truly, I say to you, today you will be with me in Paradise."
If there is any doubt about being able to do anything to merit our salvation, the thief on the cross should dispel that evil conviction. He was guilty as he himself admitted. Does asking Jesus to save us constitute doing anything worthy of salvation? No, because he could not have even done that unless God enabled him. We must remember there was another man crucified with him and Jesus. The other thief didn’t ask for forgiveness or salvation but his circumstances were the same. The difference is that God saves. The repentant thief could only do so because God gave him faith. He didn’t even have time to be baptized, yet Jesus assured him of his salvation. Nope, there is nothing we can boast about when we are saved, not even our decision to follow Jesus.
 Elvina M. Hall, “Jesus Paid It All, 1865.