John Calvin Commentary Deuteronomy 6:13

"Thou shalt fear Jehovah thy God; and him shalt thou serve, and shalt swear by his name." — Deuteronomy 6:13 (ASV)

You shall fear the Lord your God. Therefore, it is more evident why He has just declared that there is One God, namely, that He alone may be exclusively worshipped. For unless our minds are fixed on Him alone, religion is torn, as it were, into various parts, and this is soon followed by a labyrinth of errors.

But first, He calls for reverence, and then for the worship that testifies to and demonstrates it. “Fear” contains the idea of subjection, as people devote themselves to God because His awesome majesty keeps them in their rightful place. From this results worship, which is the proof of piety.

But we must observe that the fear commanded in this passage is voluntary, so that those influenced by it desire nothing more than to obey God. When I stated, therefore, that God brings us under the yoke by a sense of His power and greatness, I did not mean that a violent and servile obedience is extorted from us. I only wished to affirm that people cannot be induced to obey God until they have been subdued by fear, because their innate corruption always involves a contempt for religion and a spirit of licentiousness.

Therefore, in Jeremiah 5:22, to exhort people to fear, He displays His awesome power in restraining the strength of the sea; but this fear leads His true worshippers further. In the other passage that has been cited from Deuteronomy 10, the word cleave again confirms the truth that as soon as people turn away from God even slightly, His worship is corrupted. For this is the meaning of that union with Himself to which He calls His worshippers: that they should be, as it were, glued to Him, and should not look elsewhere.