Angels are pure souls qualified by their holiness.
Therefore we say to the Lord about them in our prayers: “Your pure angels” (in the prayer of the offerings). Also we say in the prayer of “the breaking” in the holy mass: “the holy angels”. The Bible also surnames them: “the holy angels” (Matt. 25:31).
They are holy, and do not sin although they have the freedom of will.
They have passed the examination. Those of them who have succeeded were crowned with righteousness.
That reminds us of the word of the apostle saint Paul: “I have fought the good fight, I have kept the faith. Finally, there is laid up for me the crown of righteousness, which the Lord, the righteous Judge, will give to 5 me on that Day, and not to me only but also to all who have loved His appearing” (2 Tim. 4: 6-8).
He who will obtain the crown of righteousness on the last Day, will live in righteousness in the eternity where there will be no sin anymore.
Thus the angels in their righteousness are distinguished from the wicked angels (the devils) who were tested and failed, and lost their righteousness. Therefore we liken to the angels, those who arrive at the extreme righteousness as human beings. The monks who live the life of righteousness are thus described, in their nearness to God, as being earthly angels. Thus also it was said of saint Stephanos, the first deacon, who was “full of the Holy Spirit and wisdom” and “full of faith” (Acts 6: 3,5), that “all who sat in the council, looking steadfastly at him, saw his face as the face of an angel” (Acts 6:15).
By this righteousness, they were also called: “the sons of God” (Job 1:6), “nor can they die anymore, for they are equal to the angels and are sons of God, being sons of the resurrection” (Luke 20:36).
It was said about the righteous in the Kingdom that “they neither marry nor are given in marriage, but are like angels in heaven” (Mark 12:25).
They are in perfect purity as regards the body, and they are naturally far away from corporal intercourse, but rather there is no sex and no gender in them. Being angels they live constantly in the life of the spirit, as spiritual beings, walking permanently in the spirit, without mixture with material things.