The doctrine of Mary's entrance into heaven, body and soul. As defined by Pope Pius XII in 1950, the dogma declares that "Mary, the immaculate perpetually Virgin Mother of God, after the completion of her earthly life, was assumed body and soul into the glory of heaven."
While there is no direct evidence of the Assumption in the Bible, implicitly the Church argues from Mary's fullness of grace (Luke 1:28). Since she was full of grace, she remained preserved from the consequence of sin, namely corruption of the body after death and postponement of bodily happiness in heaven until the last day.
The Church does not rely on the Scriptures for belief in Mary's Assumption. The doctrine is rather part of the oral tradition, handed down over the centuries. It was therefore certainly revealed because, in reply to the questions, the Catholic bishops of the world all but unanimously expressed the belief that this was part of the divine revelations. In explaining the grounds for the Church's belief, Pius XII singled out the fact that Mary was the Mother of God; as the body of Christ originated from the body of Mary (caro Jesu est caro Mariae); that her body was preserved unimpaired in virginal integrity, and therefore it was fitting that it should not be subject to destruction after death; and that since Mary so closely shared in Christ's redemptive mission on earth, she deserved to join him also in bodily glorification.