1 Peter 3:15 (BSB)

But in your hearts sanctify Christ as Lord. Always be prepared to give a defense to everyone who asks you the reason for the hope that is in you. But respond with gentleness and respect,

From 1 Peter 3. Also in the ESV.

Commentary on 1 Peter 3:15

• John Calvin (Reformed), Calvin's Commentaries on 1 Peter 3:15: Though this is a new precept, it yet depends on what is gone before, for he requires such constancy in the faithful, as boldly to give a reason for their faith to their adversaries. And this is a part of that sanctification which he had just mentioned; for we then really honor God, when neither fear nor shame hinders us from making a profession of our faith.
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on 1 Peter 3:8-15: The apostle here passes from special to more general exhortations. I. He teaches us how Christians and friends should treat one another. He advises Christians to be all of one mind, to be unanimous in the belief of the same faith, and the practice of the same duties of religion; and, whereas the Christians at that time were many of them in a suffering condition...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on 1 Peter 3:15: Having a good conscience,.... Meaning not the faculty of the conscience itself, which is naturally evil, and defiled with sin, and is only made good by the sanctification of the Spirit, and the sprinkling of the blood of Jesus, by which the heart is sprinkled from it, and that itself purged from dead works; but a life and conversation according to the dictates of such...
• Albert Barnes (Presbyterian), Barnes' New Testament Notes on 1 Peter 3:15: Verse 15. But sanctify the Lord God in your hearts. In this is, "sanctify the Lord of hosts himself;" that is, in that connexion, regard him as your Protector, and be afraid of him, and not of what man can do.