John Gills Exposition of the Bible Commentary - Deuteronomy 18:21
And if thou say in thine heart , &c.; Such a thought arises in the mind, and it appears to be a difficulty, and a query is made upon it: how shall we know the word which the Lord hath not spoken ? What marks, signs, and criterions are those by which it may be known that it is not a word that comes from the Lord? read more
Matthew Henry's Complete Commentary - Deuteronomy 18:15-22
Here is, I. The promise of the great prophet, with a command to receive him, and hearken to him. Now, 1. Some think it is the promise of a succession of prophets, that should for many ages be kept up in Israel. Besides the priests and Levites, their ordinary ministers, whose office it was to teach Jacob God's law, they should have prophets, extraordinary ministers, to reprove them for their faults, remind them of their duty, and foretel things to come, judgments for warning and deliverances... read more