To be registered
He was engaged.
She was expecting
ἀπογράψασθαι σὺν Μαριὰμ τῇ ἐμνηστευμένῃ αὐτῷ, οὔσῃ ἐγκύῳ.
Luke explained that Joseph went to be registered with Mary (ἀπογράψασθαι σὺν Μαριὰμ). He said that Joseph was engaged to be married, betrothed to Mary (τῇ ἐμνηστευμένῃ αὐτῷ), not yet married, but Mary was expecting or with child (οὔσῃ ἐγκύῳ), as his fiancée. The divine circumstances of that pregnancy had been laid out in the preceding chapter. Matthew pointed out in chapter 1 or his work that Joseph had been disturbed about this pregnancy. It was about an 85-mile trip from Nazareth to Bethlehem. This was the third time that Mary had made this trip from Nazareth to the Jerusalem area in the last six months, after going to visit Elizabeth in the Judean hill country outside Jerusalem, and then returning, as mentioned in the preceding chapter. On top of that, her pregnancy was near its end. Today, she would have been refused an air flight, so that this land trip of about a week would have been very dangerous for her and her child.