Be ye therefore perfect, even as your Father which is in heaven is perfect. Matthew 5:48
Clement of Rome
All the generations from Adam unto this day have passed away: but they that by God’s grace were perfected in love dwell in the abode of the pious; and they shall be made manifest in the visitation of the kingdom of God.
Though I am in chains for his sake I am the more afraid, because I am not yet perfected. But your prayer will make me perfect [unto God], that I may attain unto the inheritance wherein I have found mercy.
Clement of Alexandria
We call martyrdom perfection, not because the man comes to the end of his life as others, but because he has exhibited the perfect work of love.
And since the omnipotent God Himself “gave some apostles, and some prophets, and some evangelists, and some pastors and teachers, for the perfecting of the saints, for the work of the ministry, for the edifying of the body of Christ, till we all attain to the unity of the faith, and of the knowledge of the Son of God, to a perfect man, to the measure of the stature of the fullness of Christ;” we are then to strive to reach manhood as befits the knowledge, and to be as perfect as we can while still abiding in the flesh, making it our study with perfect concord here to concur with the will of God, to the restoration of what is the truly perfect nobleness and relationship, to the fullness of Christ, that which perfectly depends on our perfection. – ibid
For instance, on Abraham becoming a believer, it was reckoned to him for righteousness, he having advanced to the greater and more perfect degree of faith. For he who merely abstains from evil conduct is not just, unless he also attain besides beneficence and knowledge; and for this reason some things are to be abstained from, others are to be done. “By the armor of righteousness on the right hand and on the left,” the apostle says, the righteous man is sent on to the inheritance above – by some [arms] defended, by others putting forth his might. For the defense of his armor alone, and abstinence from sins, are not sufficient for perfection, unless he assume in addition the work of righteousness – activity in doing good. – ibid
Conformably, therefore, there are various abodes, according to the worth of those who have believed. To the point Solomon says, “For there shall be given to him the choice grace of faith, and a more pleasant lot in the temple of the Lord.” For the comparative shows that there are lower parts in the temple of God, which is the whole Church. And the superlative remains to be conceived, where the Lord is. These chosen abodes, which are three, are indicated by the numbers in the Gospel – the thirty, the sixty, the hundred. And the perfect inheritance belongs to those who attain to “a perfect man,” according to the image of the Lord… But “it is enough for the disciple to become as the Master,” said the Master. To the likeness of God, then, he that is introduced into adoption and the friendship of God. – ibid
“Be you perfect as your father, perfectly,” by forgiving sins, and forgetting injuries, and living in the habit of passionlessness. For as we call a physician perfect, and a philosopher perfect… Ought we not then to be perfect, as the Father wills? For it is utterly impossible for any one to become perfect as God is. Now the Father wishes us to be perfect by living blamelessly, according to the obedience of the Gospel. – ibid