Scriptural Roots of Mary's Assumption

Is the Assumption of Mary found in the Bible? Yes - but you have to connect the dots.

1. Let's begin with the Ark of the Covenant. The Ark contained the word of God, the Ten Commandments:

The Lord then wrote on the tablets, as he had written before, the ten words [i.e. the Ten Commandments] that the Lord had spoken to you on the mountain from the midst of the fire on the day of the assembly; and the Lord gave them to me. Then I turned and came down from the mountain, and placed the tablets in the ark I had made. (Deuteronomy 10:4-5)

The Ark of the Covenant was housed in the tabernacle, or tent of meeting: 

Then the cloud covered the tent of meeting, and the glory of the Lord filled the tabernacle. Moses could not enter the tent of meeting, because the cloud settled down upon it and the glory of the Lord filled the tabernacle (Exodus 40:34-35). 

In the second book of Samuel, King David seeks to bring the Ark of the Covenant to Jerusalem. He does so with holy reverence, asking, "How can the ark of the Lord come to me?” (2 Samuel 6:9). But when the time is right, David went to bring up the ark of God from the house of Obed-edom into the City of David with joy... Then David came dancing before the Lord with abandon... King David jumping and dancing before the Lord (2 Samuel 6:12,14,16). 

2. Mary is the new Ark of the Covenant.

As the Ark contained the word of God, Jesus, the eternal Word of God (John 1:1), dwells within Mary. 

As the glory of God (represented by the cloud) overshadowed the tabernacle containing the Ark of the Covenant, "the angel said to her in reply, 'The holy Spirit will come upon you, and the power of the Most High will overshadow you'" (Luke 1:35).

As David danced for joy before the Ark, "when Elizabeth heard Mary’s greeting, the infant [John the Baptist] leaped in her womb" (Luke 1:41). 

As David questioned how the Ark could come to him, so Elizabeth asked, "And how does this happen to me, that the mother of my Lord should come to me?" (Luke 1:43). 

3. The Ark appears in Heaven.

Then God’s temple in heaven was opened, and the ark of his covenant could be seen in the temple. There were flashes of lightning, rumblings, and peals of thunder, an earthquake, and a violent hailstorm. A great sign appeared in the sky, a woman clothed with the sun, with the moon under her feet, and on her head a crown of twelve stars. She was with child and wailed aloud in pain as she labored to give birth... She gave birth to a son, a male child, destined to rule all the nations with an iron rod. (Revelation 11:19, 12:1-2,5)

John sees the Ark of the Covenant in Heaven, and, lest the connection between the Ark and Mary, the new Ark, be missed, John promptly sees Mary appearing in heavenly glory in the sky. 

In John's vision we see the fulfillment of Psalm 132, which states: “Arise, Lord, come to your resting place, you and your mighty ark" (Psalm 132:8).

This is not an exhaustive survey of Biblical references to Mary's Assumption. (You can take a deeper dive with this article from Catholic Answers.) But hopefully it explains a little what the Church teaches as dogma: 

"'Finally the Immaculate Virgin, preserved free from all stain of original sin, when the course of her earthly life was finished, was taken up body and soul into heavenly glory, and exalted by the Lord as Queen over all things, so that she might be the more fully conformed to her Son, the Lord of lords and conqueror of sin and death.' The Assumption of the Blessed Virgin is a singular participation in her Son's Resurrection and an anticipation of the resurrection of other Christians: 'In giving birth you kept your virginity; in your Dormition you did not leave the world, O Mother of God, but were joined to the source of Life. You conceived the living God and, by your prayers, will deliver our souls from death.'" (1)

Notes: (1) Catechism of the Catholic Church, 966; the first quote is from Lumen Gentium, 59; the second quote is from the Byzantine liturgy for the Feast of the Dormition of Mary on August 15).  

Pray the Divine Mercy Chaplet every day for the salvation of souls.