"If the Israelites repent, they will be redeemed, but if not they will not be redeemed" (b. Sanh. 97b, R. Eliezer ben Hyrcanus, A.D. 90)
"If the Israelites would repent for a day, the son of David (messiah) would come immediately" (p. Ta'an. 1:1 [64a]).