Gregory of Nyssa

(ubi sup.) But the offspring of this birth is alone seen to be spiritually male, as contracting no guilt from being born of a woman. Hence He is truly called holy, and therefore Gabriel, as if announcing that this commandment belonged to Him only, said, That Holy thing which shall be born of thee shall be called the Son of God. Now of other first-borns the wisdom of the Gospel has declared that they are called holy from their being offered to God. But the first-born of every creature, That holy thing which is born, &c. the Angel pronounces to be in the nature of its very being holy.