Angel of the Lord

What is unique about “an angel of the Lord” (Matthew 1:20) appearing to Joseph?
While the Lord Himself appeared in a dream to a few people, including Abimelek (Genesis 20:3), Jacob (Genesis 31:13), Laban (Genesis 31:24), and Solomon (1 Kings 3:5), and an angel of the Lord appeared to many people while they were awake, Joseph is the only person to whom, the Bible explicitly says, an angel of the Lord appeared in a dream, not only above, but also to tell him to go to Egypt (see Matthew 2:13), and then to return from Egypt (see Matthew 2:19).

Why did the angel of the Lord call Joseph “son of David” (Matthew 1:20)?
Joseph is a descendant of David (see the genealogy of Jesus).

What five things did the angel of the Lord tell Joseph above?
1.  Marry Mary.
2.  The baby in her is from the Holy Spirit, not adultery.
3.  The baby is a Son.
4.  Name Him Jesus.
5.  He will save His people from their sins.

Did Joseph obey?
He “did as the angel of the Lord commanded him” (Matthew 1:24).

How does Joseph's reaction contrast with Zacharias' reaction to his encounter with an angel?
When an angel appeared to Zacharias in person, not in a dream, and told him that God will give him a son - John the Baptist - in answer to the prayers from him and his aged wife, Zacharias, who was a priest, didn't believe: And Zacharias said to the angel, “How will I know this? For I am an old man and my wife is advanced in her days” (Luke 1:18). In contrast, Joseph believed and heeded the words of the angel even though he could have dismissed the encounter as 'just a dream,' and a woman having a baby without having had sex is a more incredible miracle than an old couple having a baby.

Does that mean we should believe everything we see and hear in our dreams?
All extra-biblical messages, including those received in dreams, must be qualified through and confirmed to be consistent with the words of God in the Bible.

What traits does the Bible reveal about Joseph?
The Bible doesn't record any words spoken by Joseph, but his actions and decisions indicate the following:
1.  He loved Mary.
2.  He was righteous; even though he loved Mary, he knew right from wrong and wasn't about to turn a blind eye to what he thought was her adultery.
3.  He had mercy; because adultery was punishable by death, he was about to divorce her and send her away secretly.
4.  He had faith; a woman being pregnant without having had sex made no sense to him, but he believed God can make it happen.
5.  He was obedient; he went ahead and married Mary as commanded.