פירוש על דברים 7:9

לאלף דור TO A THOUSAND GENERATIONS — But elsewhere (5:10) it states: to thousands of generations! The explanation is: Here where it is connected with (refers to) "those who keep His commandments" it states that God's grace is extended to a thousand generations; but there where it is associated with "those who love Him" it states that it is extended to thousands of generations (Sotah 31a);

KNOW THEREFORE from the [circumstances of the] departure from Egypt THAT THE ETERNAL THY G-D, HE IS G-D Who created heaven and earth, as I have explained.³⁴²Above, 6:26. And know furthermore from this that He is THE FAITHFUL G-D Whose word shall not return void,³⁴³See Isaiah 55:11. and WHO KEEPETH THE COVENANT AND MERCY WITH THEM THAT LOVE HIM, AND KEEP HIS COMMANDMENTS, who fear His Name, TO A THOUSAND GENERATIONS of their seed, just as He kept for you the covenant of your fathers. And know further that He repayeth them that hate Him³⁴⁴Verse 10. the recompense of their wickedness to the face of each one of them to destroy them, just as He destroyed the Egyptians and did not delay [in bringing punishment] to them. Now this attribute that he mentioned is true forever. Thus although there is a wicked man that prolongeth his life in his evil-doing,³⁴⁵Ecclesiastes 7:15. it happens to him only because of this above-mentioned attribute that He is the Keeper of Mercy, and he [the wicked] has done some good which must be recompensed. If so, there are among the attributes of the Holy One, blessed be He, but two ways [of dealing with people]: He repays good for good, and evil for evil.
It is possible that those that hate Him [mentioned here as destined to be destroyed without delay] are those confirmed sinners who deny His existence and have no merit at all. As the Rabbis have said:³⁴⁶Koheleth Rabbah 7:32. “Rabbi Yashiyah said: Because of three things the Holy One, blessed be He, is long-suffering to the wicked in this world: they may repent, or they have observed commandments for which the Holy One, blessed be He, repays them their recompense in this world, or perhaps righteous people will descend from them. For so we find that He was long-suffering with Ahaz,³⁴⁷A wicked king of Judah (II Kings 16:1-5). and Hezekiah came from him; so also to Amon,³⁴⁸Ibid., 21:19-22. and Josiah came from him; and so also to Shimei,³⁴⁹The son of Gera, the Benjamite who cursed David (I Kings 28). and Mordecai came from him.”³⁵⁰Esther 2:5. Thus all these [three above categories] are not included in [the term] those that hate Him. Now there is a secret in the expression ‘el panav’ (to his face) [And He repayeth ‘them’ that hate Him ‘el panav’ — “to his face”]³⁵¹The point is that since the verse begins with the plural [‘those’ that hate Him], why does it change to the singular [to ‘his’ face, to destroy ‘him’]? Ramban alludes to the secret of the transmigration of the soul, so that at some future generation the recompense is still to “the face” of the sinner after he has been rewarded for the good he has done (Abusaula). as applying to a wicked man who has a good [i.e., a happy and prosperous] life.³⁵²Berachoth 7 a. And then he returns to say, Thou shalt therefore keep the commandment etc.,³⁵³Verse 11. meaning: “therefore keep the commandment, and the statutes, and the ordinances so that you should not be among those who hate Him, who are destroyed, but instead you should be of those that love Him and keep His commandments³⁵⁴Verse 9. who are remembered for good and for life.”
Eikev

הא-ל הנאמן, Who is constant, not subject to change.