Albert Barnes Commentary Psalms 90:13

"Return, O Jehovah; how long? And let it repent thee concerning thy servants." — Psalms 90:13 (ASV)

Return, O Lord - Come back to your people; show mercy by sparing them. It would seem probable from this that the psalm was composed in a time of pestilence, or raging sickness, which threatened to sweep all the people away — a supposition by no means improbable, as such times occurred in the days of Moses, and in the rebellions of the people when he was leading them to the promised land.

How long? - How long shall this continue? How long shall your wrath rage? How long shall the people still fall under your hand? This question is often asked in the Psalms (Psalms 4:2; Psalms 6:3; Psalms 13:1–2; Psalms 35:17; Psalms 79:5, and others).

And let it repent thee - That is, withdraw your judgments, and be merciful, as if you repented. God cannot literally “repent,” in the sense that he is sorry for what he has done, but he may act “as if” he repented; that is, he may withdraw his judgments; he may arrest what has been begun; he may show mercy where it seemed that he would only show wrath.

Concerning thy servants - In respect to your people. Deal with them in mercy and not in wrath.