וידעת כי ה' א-להיך הוא וגו' KNOW THAT THE LORD YOUR GOD ... [KEEPS HIS COVENANT AND HIS (promise of) BENEVOLENCE UNTIL THE THOUSANDTH GENERATION]: In other words, lest you say, “Since God made an oath to our forefathers to give us this land, why do we have to observe His commandments any more? Surely God will do what He promised, no matter what [we do].”
Against such thinking I [Moses] answer:
If you do not observe God’s commandments, you will not inherit the land. [And yet, even if He denies you entry into the land,] God is not reneging on His oath. For this is God’s way:1 “HE KEEPS (i.e., He waits2 [to fulfill]) HIS COVENANT AND HIS [promise of] BENEVOLENCE that He swore to the forefathers. [He would wait to fulfill it even] FOR A THOUSAND GENERATIONS; [He would wait] for that generation that would consist of THOSE WHO LOVE HIM AND KEEP HIS COMMANDMENTS.3
And this is the same idea that Moses expressed in the verse below when he concluded this theme (vs. 12), “And if you do obey these rules ... then the LORD your God will ‘keep’ for you the covenant and the [promise He made of] benevolence.” [The phrase “ושמר לך – He will keep for you,” means that] He will not wait for a thousand generations; He will keep it [i.e., fulfill it] for you.4
1. Rashbam’s language, זו היא מדתו, is a minor variation on a common rabbinic phrase about God. See e.g. Sanh. 38a (זו מדתו של הקב"ה).
2. This is the key linguistic argument of Rashbam’s comment: the verb ש-מ-ר does not always mean to observe or to fulfill. At times it means to wait, to hold something in abeyance until the appropriate time. See e.g. Rashi ad Genesis 37:11, Rashi and Rashbam ad Exodus 12:42, and note 92 on pages 122-123 of my Exodus volume.
3. Rashbam offers a unique interpretation of our verse. Almost universally this verse is seen as one that comforts the Israelites by reassuring them that God “keeps” His covenant, which will continue “for a thousand generations.” Rashbam says that the verse contains a not-so-hidden warning. God has never obligated Himself to rush to fulfill His covenant. He never promised to fulfill the covenant for any specific generation. The Israelites are still obligated to observe God’s commandments. If and only if they do that, God will fulfill His promises. Otherwise He will “keep” the covenant, i.e., He will put it on hold until an appropriate moment. In other words, Rashbam’s explanation is almost the opposite of the standard reading, which emphasizes that God is trustworthy and reliable (נאמן) to fulfill His promises; Rashbam says, on the other hand, that God is patient and could wait a long time before doing what we expect of Him. On Rashbam’s attitude to the question of the fulfillment of divine promises, see also his commentary below to 18:22, and note 37 there.
Rashbam’s explanation does not appear to be the simplest understanding of the phrase שומר הברית והחסד. Rashi does not comment on the phrase here, but he does so twice in his commentary on Kings. Ad 1 Kgs 3:6 Rashi explains the phrase the more standard way: God fulfills his words (מאמת את דבריו). However ad 1 Kgs 8:23 Rashi writes essentially what Rashbam does here: the verb ש-מ-ר implies that God delays and waits for the appropriate time to fulfill His promises.
Rashbam’s interpretation does have the benefit of explaining the way our verse is integrated into the context of our chapter, which is, like much of the book of Deuteronomy, an exhortation to observe the commandments. Few exegetes address the context question directly. Cf. R. Joseph Bekhor Shor who suggests that vs. 9 continues the thought of vs. 8, which describes the exodus from Egypt. The exodus, he argues, proves to the Israelites in the wilderness that God fulfilled promises for them in the past. That should reassure them that God would continue, in the future, to fulfill promises “for a thousand generations.” See also Ibn Ezra ad vs. 11, “Therefore observe (ושמרת) the Instruction.” According to Ibn Ezra, the Israelites are encouraged to “keep” the commandments since God will certainly “keep” His covenantal responsibilities. His interpretation is very different from Rashbam’s idea that the Israelites had better “keep” the commandments, otherwise God will delay and “keep” his covenantal responsibilities for a more worthy generation.
4. As Rashbam says above, vs. 9 means that God “holds” (שומר) the promises that he made to the forefathers, awaiting a worthy generation. Vs. 12, says Rashbam, teaches the Israelites that if they observe God’s laws, then they will one day find that the promises had been held and reserved for them (ושמר לך).
See also commentary to vs. 12 below.