1Pet 3:15

“The apostle tells us to be ready to give an answer to anyone who asks us for an explanation of our faith, because if an unbeliever asks me a reason for my faith and hope and I perceive that he cannot accept it unless he believes, I give him that very reason, so that he may see how absurd it is for him to ask a reason for things which he cannot grasp until he believes.”

“Just as magnifying God cannot add anything to his greatness and glorifying him does not make him any more glorious, so sanctifying the Lord does not mean that there is any addition to his existing holiness. Rather we are called to sanctify him in our hearts, and if we form a clear understanding of his holiness, then we do not sanctify him on one occasion only, but rather by doing this we have a better understanding of what his holiness is and something of it is implanted in our hearts. Likewise someone who magnifies God receives a share of his greatness, and someone who glorifies him is glorified in turn. It is a prophetic voice which says that there should be no fear in you which might prevent you from confessing Christ in your hearts. You should sanctify him there also. For this confession is sanctification both for the soul and for the body. Some people wonder why the Savior said: "Do not worry about what you will say," but here the apostle writes: "Be ready to give an explanation." However, there is no contradiction. Jesus was speaking about bearing witness, whereas Peter is talking about teaching others the faith.”

“Sanctify the Lord Christ in your hearts. What does it mean to sanctify the Lord in our hearts, if not to contemplate His holiness, which is of incomprehensible glory, with the innermost affection of the heart? How much strength He is able to give to those hoping in Him to overcome, whose inestimable holiness shines forth.”

“Always be prepared to provide an answer to everyone who asks you to give the reason for the hope that you have. We must be prepared to give an account of our hope and faith to those who ask in two ways, so that we may reveal the just reasons for our hope and faith to everyone, whether they inquire faithfully or unfaithfully, and so that we always hold firm the very profession of our faith and hope, even amidst the pressures of adversaries, showing by patience how reasonably we have learned to maintain it, for the love of which we neither fear to suffer adversities nor to undergo death.”

“The words "ready... to give an answer" and so forth must be connected with the words "show good conduct" ("have a good conscience"). For when you do this with meekness and propriety, then you yourselves will be assured that you have a good conscience, and you will put to shame those who have a bad opinion of you. The apostle commands the faithful person to always be ready to give an account of the faith, so that whenever anyone asks us about the faith, we may always be able to answer easily, and to do this with meekness, as indeed all things generally, as if in the presence of God Himself. For in the presence of his master, no sensible servant is insolent. The benefit of this is that the unbelievers will learn what kind of people we are and will be fair to us. It should be noted that these words of the apostle do not contradict the saying of the Lord. When the Lord says that when we are brought before rulers and authorities, we should not worry about "what we shall answer" (Luke 21:14), while Peter now commands us to prepare an answer, the Lord is speaking about testimony, whereas the apostle Peter is speaking about teaching. For whoever thinks he knows something without understanding and investigation brings reproach upon himself. For the knowledge of the foolish consists of unfathomable words. Another interpretation: Since they accused us of many lawless deeds and represented our hopes as vain, the apostle commands us to prepare well-considered answers and to have a praiseworthy life, which he also calls conscience.”

“That the Lord commands sanctification, that is, rest for the sake of loving, this is a purely moral precept. Whence blessed Peter says: But sanctify the Lord Christ in your hearts, that is, love him. For he sanctifies or makes holy the Sabbath who loves God above all things for his own sake, not for the sake of something else.”

“Furthermore, God commands "to sanctify Him in the hearts," as Isaiah says (Is. 8:13): this means, do not glory in those things that appear, but in the hidden treasury of your hearts, working the sanctification of the Lord, which consists in the separation of the nations from their abominations or wicked customs; thus sanctify Him. However, being sanctified, while others glorify Him through your good conduct, just as God and man Himself commands when He says: "Let your light shine before men," etc. (Matt. 5:16) What is said about being ready is connected to the previous part, for example, "all of you, be united." The word "be" is also attributed to the common understanding, so the meaning is: "May you always be ready." He wants to command that a faithful person should always be prepared regarding the discourse of faith, so that at any time when a reason concerning it is sought from us, we may easily respond; moreover, in responding, let us do so with meekness, as if God Himself were present: no diligent servant would be arrogant in the presence of his master. It also adds the profit that follows from this, namely, the inquiry of the unbelievers and the kindness of the mind towards us. However, it should be noted that these are not contrary to what has been said by the Lord, for He indeed commands not to be anxious about what we should answer when we are brought before rulers and authorities. (Matt. 10:19) Indeed, the Lord's words about martyrdom were spoken, as He also says that virtue and a more powerful discourse should be given than any human wisdom, and that one who despises the surrounding fears: however, Peter's opinion speaks of doctrine. For without understanding and inquiry, it is worthy of reproach to think one knows something. For the knowledge of the foolish is an unprofitable discourse. (Eccles. 21:21) Moreover, since we were accused of various wicked things, and they also showed that our hope was vain, he says that we should bring forth considered responses about these things, having at the same time a proven life, which he certainly calls conscience.”