Deuteronomy 32:4 - Matthew Poole's English Annotations on the Holy Bible

The rock, or, a rock, as for the stability and everlastingness of his nature, and invincibleness of his power, so also for his fixedness and immutability in his counsels and promises and ways; so that if there shall be a sad change in your affairs from a high and prosperous to a calamitous and deplorable condition, as there will be, remember that this proceeds from yourselves, and from the change of your ways and carriages towards God, and not from God, in whom there is no variableness nor shadow of change, James 1:17. His work is perfect; all his works and actions are unblamable, as being perfect, wise, and righteous, as it follows. All his ways are judgment; all his administrations in the world, and particularly all his dealings with you, are managed with judgment and justice. A God of truth, constant to his promises: you cannot accuse him of any levity or unfaithfulness towards you to this day.