Moses
Deuteronomy 7:9BSB·traditional attribution

Know therefore that the LORD your God is God, the faithful God who keeps His covenant of loving devotion for a thousand generations of those who love Him and keep His commandments.

John Calvin Reformed @genevareformer

9. Know therefore that the Lord thy God, he is God. The verb “Heb. And thou shalt know.” — Ainsworth. “Et scies.” — V. might have been as properly translated in the future tense; and, if this be preferred, an experimental knowledge, as it is called, is referred to, as if he had said that God would practically manifest how faithful a rewarder He is of His servants.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. A very strict caution against all friendship and fellowship with idols and idolaters. Those that are taken into communion with God must have no communication with the unfruitful works of darkness. These things they are charged about for the preventing of this snare now before them. 1. They must show them no mercy, Deu 7:1, Deu 7:2.

Commenting on Deuteronomy 7:1-11

John Gill Reformed Baptist @doctorgill

The only true and living God, and not the idols of the Gentiles, who are false and lifeless ones, and therefore not the proper objects of adoration: the faithful God, which keepeth covenant and mercy; as appeared by fulfilling the promise made to their fathers, in bringing them out of Egypt, and now them to the borders of the land of Canaan given them for...