Albert Barnes Commentary Matthew 27:42-43

"He saved others; himself he cannot save. He is the King of Israel; let him now come down from the cross, and we will believe on him. He trusteth on God; let him deliver him now, if he desireth him: for he said, I am the Son of God." — Matthew 27:42-43 (ASV)

He saved others. It does not seem probable that they meant to admit that he had actually saved others, but only that he pretended to save them from death by miracles, or that he claimed to be the Messiah and thus affirmed that he could save them. This is therefore cutting irony.

If he be the King of Israel, and so on. It may seem strange to some that Jesus did not vindicate by a great miracle his claims to be the Messiah, and come down from the cross. But the time had come for him to make atonement. He had given full and sufficient proof that he was the Christ.

The people would have been no more satisfied that he was the Messiah, if he had come down from the cross. They said this for the purpose of insult; and Jesus chose rather to suffer, though his character was assailed, than to work a new miracle for their gratification. He had foretold his death, and the time had come; and now, amidst revilings, and jibes, and curses, and the severe sarcasms of an angry and apparently triumphant priesthood, he chose to die for the sins of the world.

To this they added insult to God, profanely calling upon Him to interpose by miracle and save Jesus, if He was his friend. And all this, when their prophets had foretold this very scene, and when they were fulfilling the predictions of their own Scriptures. So wonderful is the way by which God causes His word to be fulfilled.

"he said I" (John 5:17–18; John 10:30, 36).