Deuteronomy 23:7,8

Thou wast a stranger And didst receive habitation, protection, and provision from them a long time, which kindness thou must not forget for their following persecution. It is ordinary with men that one injury blots out the remembrance of twenty favours. But God doth not deal so with us, nor will he have us to deal so with others, but commands us to forget injuries, and to remember kindnesses. In the third generation When they had been proselytes to the true religion for three generations, they might be incorporated with the Jewish community. And, according to the Hebrew masters, the grand-children are the third generation.