10 Take good heed then, Beloved: “Go,” says He, “sell all that you have, give to the poor, and you shall have treasure in heaven, and come, follow Me.” Peter is perfect, now that the Lord sits in heaven at the right Hand of the Father, then did he attain perfection and maturity. For when he followed the Lord to His Passion, he was not perfect; but when there began to be no one on earth for him to follow, then was he perfected. But you truly have always One before you to follow; the Lord has set up an example on earth, when He left the Gospel with you, in the Gospel He is with you.
For He did not speak falsely when He said, “Lo, I am with you always, even unto the end of the world.” Therefore follow the Lord. What is, “Follow the Lord”? Imitate the Lord. What is, “Imitate the Lord”? “Learn of Me, that I am meek and lowly in heart.” Because if I should distribute all my goods to the poor, and give up my body to be burned, but not have charity, it profits me nothing. To this charity then I exhort your Charity; now I should not exhort to charity, but with some charity.
I exhort then that what is commenced may be filled up; and pray that what is begun may be perfected. And I beg that you would offer this prayer for me, that what I advise may be perfected in me also. For we are all now imperfect, and there shall we be perfected, where all things are perfect. The Apostle Paul says, “Brethren, I do not reckon myself to have apprehended.” He says, “Not that I have already attained, either am already perfect.” And shall any man dare to vaunt himself on perfection? Yea rather let us acknowledge our imperfection, that we may attain perfection.
Source: Sermons on Selected Lessons of the New Testament (New Advent)