We are not certain from the Holy Scripture the exact time and circumstances of the institution of Holy Mooron. According to Acts 1:2, before his Ascension

Our Lord appeared to the Apostles and taught them regarding the Kingdom (the Church). 

Rev.P.E Warren in his book says: "The institution may have been included among the things about the Kingdom of God which our Lord spoke to the Apostles during the 40 days Act 1:3. for we find the Apostles employing it immediately afterward".

According to the tradition of the Church, the apostles consecrated the Holy Mooron, on Monday after the Pentecost Sunday using olive oil and myrrh and aloes with which our Lord was embalmed. (which they had gathered from the empty tomb)

Anointing by Holy Mooron (confirmation) is the Sacrament by which the Holy Spirit, in an unseen manner seals. the Holy Spirit comes to each person to abide with him. The anointing of the Holy Mooron, like Baptism, may be received only once. Once we have been made the Children of God, we remain so always, and when we receive the Holy Spirit we receive Him once and for all. 

We may indeed become unloving and disobedient children, and we may grieve the Holy Spirit by neglecting to use the powers and Grace given to us. But by repentance and Confession, the hindrance to God's Grace which our sinfulness has to cause is removed.

As stated above, our practice of anointing immediately after Baptism is Apostolic and ancient.

 Tertullian in the 2nd. century says " After this, having come out from the bath, we are anointed with a blessed unction according to the ancient rule..." St. Cyprian says " Whoso has been Baptised must also need to be anointed, that having received the Chrysm ie.. the anointing, he may be the anointed of God and within him the Grace of God."

"The ancient custom that continued in the Eastern Churches was to administer it to the infants. In the West, it became usual during the Middle Ages to postpone it to the Age of Reason." Again in the primitive Church, confirmation as the preliminary to Holy Communion followed closely upon Baptism both in the case of infants and adults. The confirmation of the infants is still the practice of the Eastern Churches.

By the anointing of the Holy Mooron, the Baptised receives the seal of eternal. The Mooron is defined as the fragrance of Christ. The mark and seal of true Faith, and the perfection of the Holy Spirit. It is being anointed i. for life eternal. 2 To receive the seal of the soldier of Christ, 3. to overcome the hostile powers, and 4. to walk in the light of God's commandments.

In Old Testament times, Priests and kings were anointed with Holy Oil. (Lev. 6:20, 8:10, 10:7, 1 Sam.10:3, 16:18, 1 Kin. 1:39) The Tabernacle, the Table of Shew-bread, and the altar of the burnt offering were also anointed. The Lord commanded Moses to consecrate the Holy Oil. (Ex. 30:22)

In the New Testament times the 22nd. Cannon of the Apostles:- "Those who are being Baptised should be anointed with blessed oil first, then Baptism with water, and finally with Holy Mooron."