John Calvin Commentary Psalms 105:43

"And he brought forth his people with joy, [And] his chosen with singing." — Psalms 105:43 (ASV)

And he brought forth his people with joy. The prophet mentions joy and gladness to magnify more highly the greatness of God’s grace.

It was no small matter that at the very time when the Egyptians were afflicted by a severe and dreadful plague—when the whole kingdom was full of weeping and howling, and when in almost every house there was a dead body—the people who shortly before were groaning in great distress, or rather lay almost dead, went out with joyful hearts.

By the designation the chosen of God, they are reminded that His favor was not shown to them in this way because of their own merits or because of the worth of their lineage, but because He had adopted them, so that people, having nothing left in which to boast, might learn to glory in God alone.