19 Then you will say, “The branches were broken off so that I could be grafted in.” 20 Granted! They were broken off because of their unbelief, but you stand by faith. Do not be arrogant, but fear! 21 For if God did not spare the natural branches, perhaps he will not spare you. 22 Notice therefore the kindness and harshness of God—harshness toward those who have fallen, but God’s kindness toward you, provided you continue in his kindness; otherwise you also will be cut off. 23 And even they—if they do not continue in their unbelief—will be grafted in, for God is able to graft them in again. 24 For if you were cut off from what is by nature a wild olive tree, and grafted, contrary to nature, into a cultivated olive tree, how much more will these natural branches be grafted back into their own olive tree?
Kiddushin 36aBabylonian Talmud
And if you would say: It is when they do not have faithfulness that they are called sons, as stated, but when they worship idols they are not called sons anymore; therefore, come and hear: And the verse states: “A seed of evildoers, sons who deal corruptly,” which alludes to the corruption of idol worship. And if you would say that although they are called “sons who deal corruptly,” they are no longer called full-fledged sons of God once they have sinned, come and hear: And the verse states: “And it shall come to pass that, instead of what was said to them: You are not My people, it shall be said to them: Sons of the living God.” This verse indicates that when the Jews repent they are again called full-fledged sons of God.
Notes and References
"... In spite of what might initially seem to be the meaning of the 'on condition that' passages — that God would cancel the covenant if its conditions were not fulfilled — there is actually no hint of such a view in the entire body of Tannaitic literature. The 'on condition that' passages themselves are not directed toward such a possibility. Partially, they are hortatory, insisting that the named commandment should be observed. The primary intention, however, is to emphasize that anyone wishing to deny the implications of the covenant — the obligation to keep its commandments — is considered to be rejecting the covenant itself, essentially 'denying the exodus.' While such a person may choose to withdraw from the covenant, this does not imply cancellation on God's part. The Rabbis never doubted that God would remain faithful to the covenantal promises, even when met with disobedience. This universal view is distinctly stated by R. Jose (b. Halafta): 'No word of blessing that issued from the mouth of the Holy One, blessed be He, even if based upon a condition, was ever withdrawn by Him.' This point is elaborated in the Mekilta, where R. Eleazar b. R. Jose says in the name of Abba Jose the son of the Damascene: "And God saw the children of Israel," knowing that they would provoke Him in the future; 'and God took cognizance of them,' knowing that they would blaspheme in the future. So why was He so lenient? Because of the power of repentance. Similarly, why does it say that "He was their Savior" (Isaiah 63.8) when He knew that Israel would deal falsely with Him? Because 'He, being full of compassion, forgives iniquity' (Psalm 78:38). The only possible exception to this view — that God maintained the promises of the covenant despite disobedience — is a remark attributed to R. Judah (Sifre Deuteronomy 96 (157; to 14.1); compare Kiddushin 36a) ..."
Sanders, E. P. Paul and Palestinian Judaism: A Comparison of Patterns of Religion (p. 95) Fortress Press, 1977