Albert Barnes on 1 Peter 1:15

But as he which hath called you is holy. On the word called, Eph 4:1. The meaning here is, that the model or example in accordance with which they were to frame their lives, should be the character of that God who had called them into his kingdom. They were to be like him. Comp. Mt 5:48.

So be ye holy in all manner of conversation. In all your conduct. On the word conversation, Php 1:27. The meaning is, that since God is holy, and we profess to be his followers, we ought also to be holy.