Jerome

And you, sons of Jacob, were not consumed. For from the days of your fathers, you have strayed from my commandments and have not kept them. LXX: And you, sons of Jacob, have not strayed from the sins of your fathers, you have turned away from my commandments, and have not kept them. As I said before: I will be a swift witness against sorcerers, adulterers, perjurers, those who exploit hired workers, widows and orphans, and those who oppress the foreigners, for they have not feared me, says the Lord of hosts. …

Commentary on Malachi ↗

Hilary of Poitiers

He does not lack things that are of Him and through Him and in Him. The Source and Maker of all, Who contains all, Who is beyond all, does not need that which is within Him, the Creator His creatures, the Possessor His possessions. Nothing is prior to Him, nothing derived from any other than Him, nothing beyond Him. What element of fulness is still lacking in God, which time will supply to make Him all in all? Whence can He receive it, if outside Him is nothing, and while nothing is outside Him, He is eternally Himself? …

On The Trinity 11:47 ↗

Bonaventure

That the divine being is immutable is shown thus: First, by authority, Malachi 3: I am God and I do not change: the Gloss says: "He says this lest it be thought that there is any mutability in God." It must be said that without doubt the divine being is altogether immutable: and this indeed must be maintained, although we cannot perfectly understand it; whence all agree in maintaining it. …

Quaestiones Disputatae, De Mysterio Trinitatis, Question 6 ↗