1 Peter 1:15

But as he which hath called you is holy
Which is a periphrasis of God the Father, who had called them, not merely in an external way, by the outward ministry of the word; but internally, powerfully, and efficaciously, by his Spirit and grace; and who had called them to holiness of life and conversation, as well as in calling had implanted principles of holiness in them, and therefore is said to call them with an holy calling; and who himself is holy, naturally, perfectly, and originally, and in such sense as no creature is, angels or men; and is glorious in holiness, and is the source and fountain of holiness in others: therefore

[so] be ye holy in all manner of conversation;
which respects not internal holiness, but supposes it; for that is God's work, and not the creature's act; it is the sanctification of the Spirit, of which he is the author; this they were chosen unto from the beginning, and made partakers of in regeneration; but external holiness, holiness of life and conversation, in all the parts and branches of it, both with respect to God and men, in matters both of religion and civil life: and to be holy in this sense is an imitating of God, a copying after him, though he is far from being equalled by a sinful creature, or even by an angel in heaven; however, the arguments to it, taken from the nature of God, and of his effectual calling to grace and holiness, are very strong and powerful; for it is walking worthy of him, who has called us to his kingdom and glory; and walking worthy of that calling wherein we are called; and a following of God, as dear and obedient children; and what is according to his will, and what he directs unto, and requires, as appears from what follows.