Matthew Poole and continuators on Deuteronomy 30:14

14 But the word is very nigh unto thee, in thy mouth , and in thy heart that thou mayest do it.

Thou knowest it so well, that it is the matter of thy common discourse, thou professest thy knowledge and belief of it: or, in the mouths of thy Priests and Levites, who are dayly preaching of it, and instructing thee in it.

(i. e.) In thy mind, as the heart is very commonly taken, to understand and believe it.