This is another of the verses of remembrances recited as part of the Rosh Hashana musaf service. The Radak explains this verse as follows: G-d is telling the Jews, “Even though I must bring bad things upon you because of your evil deeds, I will not allow you to be destroyed. Not only that, I will punish those who harm you. I do this because of the love you showed Me when you agreed to follow Moses and Aaron for 40 years in the wilderness, in a place where there was no food.”