Deuteronomy 6:20

“And when thy son asketh thee in time to come, etc.] Or “tomorrow” f70; that is, in later times, as Jarchi interprets it; any time after this, and particularly after they were come into the land of Canaan, when the several laws, statutes, and ordinances appointed, would take place and be obeyed: what [mean] the testimonies, and the statutes, and the judgments, which the Lord our God hath commanded you? what is the reason of the various rites, customs, and usages, the observance of which is directed to, such as the feasts of passover, pentecost, tabernacles, sacrifices, and other duties of religion? Ver. 21 Then shall thou say unto thy son, etc.] In order to lead him into the spring and…”

“when thy son asketh thee in time to come, saying--The directions given for the instruction of their children form only an extension of the preceding counsels. Next: Deuteronomy Chapter 7”

“The Israelites were at the point of quitting a normal, life for a fixed and settled abode in the midst of other nations; they were exchanging a condition of comparative poverty for great and goodly cities, houses and vineyards. There was therefore before them a double danger; (1) a God-forgetting worldliness, and (2) a false tolerance of the idolatries practiced by those about to become their neighbors. The former error Moses strives to guard against in the verses before us; the latter in Deuteronomy 7:1-11. Deuteronomy 6:13 The command “to swear by His Name” is not inconsistent with the Lord’s injunction Matthew 5:34, “Swear not at all.” Moses refers to legal swearing, our Lord to swearing…”

“when thy son: Deu 6:7; Exo 12:26, Exo 13:14; Jos 4:6, Jos 4:7, Jos 4:21-24; Pro 22:6 in time to come: Heb. to-morrow Deuteronomy 6:21”

“In Deu 6:20-25, the teaching to the children, which is only briefly hinted at in Deu 6:7, is more fully explained. The Israelites were to instruct their children and descendants as to the nature, meaning, and object of the commandments of the Lord; and in reply to the inquiries of their sons, to teach them what the Lord had done for the redemption of Israel out of the bondage of Egypt, and how He had brought them into the promised land, and thus to awaken in the younger generation love to the Lord and to His commandments. The "great and sore miracles" ( Deu 6:22) were the Egyptian plagues, like מפתּים, in Deu 4:34. \- "To fear," etc., i.e., that we might fear the Lord. Deuteronomy 6:25”