A. When you've slept enough & need to rise:

ISA 50:4. The Lord GOD hath given me the tongue of the learned, that I should know how to speak a word in season to him that is weary: he wakeneth morning by morning, he wakeneth mine ear to hear as the learned.

ZEC 4:1. And the angel that talked with me came again, and waked me, as a man that is wakened out of his sleep.

B. To flee danger:

MAT 2:13. And when they were departed, behold, the angel of the Lord appeareth to Joseph in a dream, saying, Arise, and take the young child and his mother, and flee into Egypt, and be thou there until I bring thee word: for Herod will seek the young child to destroy him.

MAT 2:14. When he arose, he took the young child and his mother by night, and departed into Egypt:

ACT 12:4. And when he had apprehended him, he put him in prison, and delivered him to four quaternions of soldiers to keep him; intending after Easter to bring him forth to the people.

ACT 12:5. Peter therefore was kept in prison: but prayer was made without ceasing of the church unto God for him.

ACT 12:6. And when Herod would have brought him forth, the same night Peter was sleeping between two soldiers, bound with two chains: and the keepers before the door kept the prison.

ACT 12:7. And, behold, the angel of the Lord came upon him, and a light shined in the prison: and he smote Peter on the side, and raised him up, saying, Arise up quickly. And his chains fell off from his hands.

C. To give you something you need:

1KI 19:5. And as he lay and slept under a juniper tree, behold, then an angel touched him, and said unto him, Arise and eat.

1KI 19:6. And he looked, and, behold, there was a cake baken on the coals, and a cruse of water at his head. And he did eat and drink, and laid him down again.

1KI 19:7. And the angel of the LORD came again the second time, and touched him, and said, Arise and eat; because the journey is too great for thee.

D. He awakens you after giving you an important message: