The [things] which the Lord said to Moses after the victory are three. The first (v. 14): “Write this, for a memorial, in a book.” See how pleasing to God [it is] that his benefits and works be commemorated by us — not by words among those present only, but also by writings among posterity; how necessary [it is] that the memory of them be kept perpetually. Hence, too, about the same history it is said (Deuteronomy 25, and Judith 4): “Remember.” The true [things], indeed — which [I have noted] on Tobias 12, and in book 3, [on] the doxologies of the Most Holy Trinity — about the narrations and writings of divine and useful things, [are] noted by me. “Let this be written,” says David (Psalm 101:19), “unto another generation: and the people that shall be created shall praise the Lord.”
(col. 83)
But here there can be three questions. The first. [Since] by other writing [the rest of the Pentateuch] Moses [wrote] without God’s [express] command — or, if by command: why is this [particular thing] now commanded? Moses did not write all [things] by the express command of God, but [only] certain [things]; all the rest [he wrote] by his instinct and direction alone. But it sometimes happened that, if Moses had wished to follow his own opinion, he would have omitted certain things — especially those which seemed joined with some praise of himself, as [is] that which [is] in this place, about his victory obtained by [his] prayers. But to write [this], not only the inner inspiration of God impelled him, but also a precept and command; and likewise the highest utility which was to flow forth from it. Rupert (book 3 On the Victory, ch. 23) gathers from this [that Moses was] commanded to write also “In the beginning God created heaven and earth.” The second question is: what book [was it] into which the Lord commanded these [things] to be entered? Abenezra [Ibn Ezra] and Abulensis think [it] is that book which is called [the book] of the Just [Jasher] (Joshua 10; 2 Kings [Samuel] 1). Others [think it] some book in general — as is signified in the Seventy [Septuagint], εἰς βιβλίον. But because in the Hebrew we read not bésepher [into a book], but, with the article, bassépher [into the book], [it is] certain; and we shall more conveniently take [it as] a definite book — and that either that [book] of the Just, or this very [book] of Exodus, which perhaps was then under Moses’s hands. The third [question]: where and when did the Lord say these [things] to Moses? Either on the mountain itself, in the evening before Moses descended, when the victory was now being fully proclaimed; or certainly on the next day, when he was in the camp, and was pouring out [his] daily prayers. The Israelites, in R. Eliezer (ch. 44), raise a fourth question: since it is said of the Sabbath day, “Remember,” how is the same now said of the Amalekites? But Moses answers: that “Remember” [about the Sabbath] is unto keeping and sanctifying; but this [about Amalek] unto destroying and blotting out — “just as,” he says, “a cup of spiced wine or mead, and a cup of vinegar, are both indeed cups”: but their taste and effect [are] different.