It is the LORD who goes before you. He will be with you; he will not leave you or forsake you. Do not fear or be dismayed.”
Loth to part (we say) bids oft farewell. Moses does so to the children of Israel: not because he was loth to go to God, but because he was loth to leave them, fearing that when he had left them they would leave God.
Commenting on Deuteronomy 31:1-8
And Moses wrote this law,.... The book of Deuteronomy, or the Pentateuch, the five books of Moses, which he had now finished, and which all of them together are sometimes called the law, Gal 4:21, and delivered it unto the priests, the sons of Levi; who were the teachers of the law, as Aben Ezra observes; see Mal 2:7; and therefore it was proper to...
And the LORD, he [it is] that doth go before thee; he will be with thee, he will not fail thee, neither forsake thee: fear not, neither be dismayed. (d) Signifying that man can never be of good courage, unless he is persuaded of God's favour and assistance.