And he said unto Jesus, Lord, remember me when Thou comest into Thy kingdom. And Jesus said unto him, Verily I say unto thee, Today shalt thou be with Me in paradise. – Luke 23:42, 43

It is not only the weakness of our Lord which makes the salvation of the penitent thief memorable; it is the fact that the dying malefactor saw it before his very eyes. Can you put yourself into his place, and suppose yourself to be looking upon one who hangs in agony upon a cross? Could you readily believe Him to be the Lord of glory, who would soon come to His kingdom? That was no mean faith which, at such a moment, could believe in Jesus as Lord and King. If the apostle Paul were here and wanted to add a New Testament chapter to the eleventh of Hebrews, he might certainly commence his instances of remarkable faith with this thief, who believed in a crucified, derided, and dying Christ, and cried to Him as to one whose kingdom would surely come. The thief’s faith was the more remarkable because he was himself in great pain and bound to die. It is not easy to exercise confidence when you are tortured with deadly anguish. Our own rest of mind has at times been greatly hindered by pain of body. When we are the subjects of acute suffering it is not easy to exhibit that faith which we fancy we possess at other times. This man, suffering as he did, and seeing the Saviour in so sad a state, nevertheless believed unto life eternal. Herein was such faith as is seldom seen…Like a jutting rock, standing out in the midst of a torrent, he declared the innocence of the Christ whom others blasphemed. His faith is worthy of our imitation in its fruits. He had no member that was free except his tongue, and he used that member wisely to rebuke his brother malefactor and defend his Lord. His faith brought forth a brave testimony and a bold confession…Behold the power of that divine Spirit who could produce such faith on soil so unlikely, and in a climate so unpropitious. ~ C.H Spurgeon

https://www.blueletterbible.org/comm/spurgeon_charles/sermons/2078.cfm