The Assumption has been believed and celebrated since the earliest times of Christianity. The feast was celebrated under various names (Commemoration, Dormition, Passing, Assumption) from at least the fifth or sixth century. Homilies concerning the Assumption go back to at least the Sixth Century. However, in order to make it a dogma of the faith meaning all Catholics must believe it, Pope Pius XII dogmatically declared Mary’s Assumption into Heaven in 1950:
“… by the authority of our Lord Jesus Christ, of the Blessed Apostles Peter and Paul, and by our own authority, we pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory” (Munificentissimus Deus)
Gen. 5:24, Heb. 11:5 - Enoch was bodily assumed into heaven without dying. Would God do any less for Mary the Ark of the New Covenant?
2 Kings 2:11-12; 1 Mac 2:58 - Elijah was assumed into heaven in fiery chariot. Jesus would not do any less for His Blessed Mother.
Psalm 132:8 - Arise, O Lord, and go to thy resting place, thou and the Ark (Mary) of thy might. Both Jesus and Mary were taken up to their eternal resting place in heaven.
2 Cor. 12:2 - Paul speaks of a man in Christ who was caught up to the third heaven. Mary was also brought up into heaven by God.
Matt. 27:52-53 - when Jesus died and rose, the bodies of the saints were raised. Nothing in Scripture precludes Mary’s assumption into heaven.
1 Thess. 4:17 - we shall be caught up in the clouds to meet the Lord in the air and so we shall always be with the Lord.
Rev. 12:1 - we see Mary, the “woman,” clothed with the sun. While in Rev. 6:9 we only see the souls of the martyrs in heaven, in Rev. 12:1 we see Mary, both body and soul.
2 Thess. 2:15 - Paul instructs us to hold fast to oral (not just written) tradition. Apostolic tradition says Mary was assumed into heaven. While claiming the bones of the saints was a common practice during these times (and would have been especially important to obtain Mary’s bones as she was the Mother of God), Mary’s bones were never claimed. This is because they were not available. Mary was taken up body and soul into heaven.
Do you really seek to undestand this teaching? If so, pick up a copy of “Hail, Holy Queen” by Scott Hahn, a former protestant minister who is a Scriptural Expert.