The answer is: In a dream

Matt 2:13 - The angel only appeared to Joseph in a dream and didn't actually visit them in a physical sense. Also the angel appeared only to Joseph and not to them both.

In the dramatic story of Jesus' early life, we find a dream playing a crucial role in safeguarding His future. Imagine being Joseph, sound asleep, when suddenly an angelic warning pierces through the night. This dream is no ordinary sleep vision; it’s a divine message, a protective whisper guided by a higher power. Interestingly, dreams as a method of revelation crop up frequently throughout the Bible. Think of Jacob’s ladder or the dreams of Pharaoh in the story of Joseph!

Now, the focus here is on Joseph. It’s worth pondering why the angel chose to reveal this crucial information only to him. Joseph's role as the earthly guardian of Jesus is profound. He exhibits traits of integrity and obedience without question, throwing light on the importance community lays on responsible paternal figures in ancient times—light often overlooked in modern narratives.

Also, remember that the looming threat came from King Herod—a ruler infamous for his ruthless paranoia who massacred innocents to secure his throne. This stark contrast between earthly authority and divine oversight resonates through the ages. The fledgling family’s journey to safety into Egypt becomes quite literal, bringing to mind ancestral themes of migration and protection found throughout the Hebrew Scriptures. From the Israelite exodus to this angel-guided flight-like journeys reflect deep rivers of faith amid uncertainty that echo through both history and modern human experience.