Charles Ellicott Commentary Deuteronomy 11:18

"Therefore shall ye lay up these my words in your heart and in your soul; and ye shall bind them for a sign upon your hand, and they shall be for frontlets between your eyes." — Deuteronomy 11:18 (ASV)

Therefore you shall lay up these my words. —The same injunctions are found above (Deuteronomy 6:6–9). The Jewish commentator remarks, somewhat sadly, here, that they would remember them in their captivity, if not before.

The "therefore" at the beginning of the verse is a simple "and," so that the passage can be read in connection with what precedes: You will perish quickly from off the good land, and you will lay these my words to your hearts.

But the words of Deuteronomy 11:21 seem to show that this is not the primary meaning—only an application suggested, like many other applications of Scripture, by the actual event.