Matthew 18:21,22 - Coke's Commentary on the Holy Bible

Then came Peter—and said, Lord, how oft, &c.— If my brother repeatedly trespass against me; how often must I forgive him? Campbell. When our Saviour had given his advice for the accommodation of differences among his disciples, Peter, imagining that it might be abused by ill-disposed persons, as an encouragement to offer injuries to others; asks his Lord, how often his brother might offend, and claim forgiveness? See Luke 17:4 where it is seven times in a day, which implies very often. Here it is seven times only, a mode of expression which some imagine to have been borrowed from the Jewish tradition, by which the necessity of pardoning in lighter matters, is limited to seven times, and no more. In opposition to this tradition, our Lord may be understood as extending the terms of forgiveness, and ordering that pardon should be repeated as often as the injury,—till seventy times seven,—as often as there is occasion; a certain number for an uncertain. See Grotius and Wetstein.