Commentary for Deuteronomy 11:22

שמר תשמרון [IF] YE SHALL DILIGENTLY OBSERVE [ALL THESE COMMANDMENTS] — The repetition of the verb implies an admonition to be very much on one’s guard: to be careful in respect to one’s study of the Torah that it should not be forgotten (cf. Sifrei Devarim 48:2).

AND TO CLEAVE UNTO HIM. Rabbi Abraham ibn Ezra commented: “[You are to walk in His ways so that you will merit to cleave unto Him] ultimately, this being a great secret.” But the secret is not by reason of this reference [here in the verse before us].³⁴²Ibn Ezra was of the opinion that this verse constitutes an assurance to the soul that it will ultimately cleave unto G-d. To this Ramban replies: “The secret itself is true, but the assurance is not from this verse, for the intent of the verse is an admonition,” as will be explained. See my Hebrew commentary p. 395. Perhaps he is stating: “to love the Eternal, to walk in all His ways until you become worthy to cleave unto Him in the end” [as Ibn Ezra wrote]. But in the Book of Joshua it is stated, Neither make mention of the name of their gods, nor cause to swear by them, neither serve them, nor worship them; but cleave unto the Eternal your G-d, as ye have done unto this day³⁴³Joshua 23:7-8. [thus indicating that “cleaving to G-d” was not an ultimate goal, but something they had been experiencing all along]. If so, the verse [before us] is one of the admonitions against idolatry, meaning that one’s thought should not part from G-d [and transfer] to other gods, that one should not think that there is any substance to idolatry but instead it is all nought and worthless. Thus this verse is similar to what he said, and Him shall ye serve, and unto Him shall ye cleave,³⁴⁴Further, 13:5. the intent being to warn that one is not to worship G-d [in combination] with anything besides Him, but to worship [only] G-d alone, with one’s heart and deeds.
It is possible that the term “cleaving” includes the obligation that you remember G-d and His love always, that your thought should never be separated from Him when thou walkest by the way, and when thou liest down, and when thou risest up³⁴⁵Verse 19. to such a degree that [a person] during his conversation with people by mouth and tongue, his [entire] heart will not be with them, but instead be directed towards G-d. With men of such excellence it is possible that even in their lifetime, their souls shall be bound in the bundle of life,³⁴⁶I Samuel 25:29. since their very being is a “residence” for the Divine Glory, as the author of the Book of the Kuzari alludes.³⁴⁷Al Khazari III. 1, by Rabbi Yehudah Halevi. I have already mentioned this matter in the section on forbidden relations.³⁴⁸Leviticus 18:4 (Vol. III, pp. 245-246). And when Joshua said as ye have done unto this day³⁴³Joshua 23:7-8. he meant, that when they were in the wilderness and the cloud of the Eternal was over them,³⁴⁹Numbers 10:34. and the manna would descend from heaven, and the quail would come up and the well was always before them, and all their requirements were provided by Heaven in miraculous ways — then their thoughts and deeds were [perforce] always with G-d. Therefore Joshua warned them that even now in the Land, when these wonderful deeds would be removed from them, their thoughts should always be with them [i.e., the wonders that G-d had done for them], to cleave unto the glorious and fearful Name³⁵⁰Further, 28:58. and their attention should not be withdrawn from Him.

כי אם שמור תשמרון לאהבה, the thrust of your preoccupation with Torah is to be that you show the acts of loving kindness G’d has performed, which in turn will ensure that you love Him.