"Little children," says our teacher, "a little while longer I am with you." That is why Paul also instructs the Galatians in these words: "My little children, with whom I travail in birth again until Christ be formed in you." And again he writes to the Corinthians: "For though you may have ten thousand instructors in Christ, yet you have not many fathers. For in Christ I have begotten you through the gospel." On this account "a eunuch shall not enter into God's assembly," that is, the man who is unproductive and unfruitful both in conduct and in word; but blessed are those who have made themselves eunuchs, free from all sin, for the sake of the kingdom of heaven by their abstinence from the world.
Source: The Stromata Book 3