St. Augustine
Let Christ be formed in you
 

    The Apostle says, Be like me, for though born a Jew, by reason of spiritual discernment I now consider carnal things of small importance. And he adds, For I am as you are, that is to say: For I, like you, am a man. Then he tactfully reminds them of his love so that they will not look on him as an enemy: Brothers, I beseech you, he says, you did me no wrong, as if to say, "Do not imagine that I want to wrong you." And to have them imitate him as they would a parent, he addresses them as little children: My little children, with whom I am again in labor until Christ be formed in you. Actually he is here speaking more in the person of Mother Church that his own. So too he says elsewhere: I was gentle among you like a nurse fondling her little ones.
    Christ is formed in the believer by faith of the i8nner man, called to the freedom that grace bestows, meek and gentle, not boasting of nonexistent merits, but through grace making some beginning of merit. Hence he can be called "my least one" by him who said: Inasmuch as you did it to the least of my brethren you did it to me.
    Christ is formed in him who receives Christ's mold, who clings to him in spiritual love. By imitating him he becomes, as far as is possible to his condition, what Christ is. John says: He who remains in Christ should walk as he did.
    Children are conceived in order to be formed in their mother's womb, and when they have been so formed, mothers are in travail to give them birth. We can thus understand Paul's words: With whom I am in labor until Christ be formed in you. By labor we understand his anxiety for those with whom he is in travail, that they be born unto Christ. And he is again in labor when he sees them in danger of being led astray. These anxieties, which can be likened to the pangs of childbirth, will continue until they come to full age in Christ, so as not to be moved by every wind of doctrine.
    He is not therefore talking about the beginnings of faith by which they were born, but of strong and perfect faith when he says: With whom I am again in labor until Christ be formed in you. He also refers elsewhere in different words to his being in labor, when he says: There is the daily pressure upon me of my anxiety for all the churches. Who is weak and I am not weak? Who is made to fall, and I am not indignant?