Fulgentius of Ruspe on Rev. 3:19: Those whom I love, I reprove and discipline, so be zealous and repent.

“The kindness of God leads us to penance. He afflicts us with trials, he corrects us with infirmities, teaches us with cares, so that we who have sinned in the health of the body may learn to abstain from sins in infirmity. We who scorned the mercy of God in frivolity, corrected by the lash of sadness should fear his justice. Thus it comes about that we who by abusing health have begotten infirmity for ourselves, through that infirmity may again procure the benefits of health. And we who through frivolity have fallen into trials, through these trials may regain happiness. Holy Scripture bears witness that God’s love for us is shown more by the lash and correction. For it says, “My child, do not despise the Lord’s discipline or be weary of his reproofs, for the Lord reproves the one he loves, as a father the son in whom he delights.”vAnd the Savior himself says that he loves those he reproves, saying, “Those whom I love, I reprove and chastise.” The teaching of the apostles does not cease to proclaim that “it is necessary for us to undergo many hardships to enter the kingdom of God.” The Lord himself also says that the road which leads to life is constricted and the gate narrow.”

— Fulgentius of Ruspe, LETTER 7.16, TO VENANTIA.40

William C. Weinrich, Revelation, Ancient Christian Commentary on Scripture NT 12, 53 (Downers Grove, IL: InterVarsity Press, 2005).