Why hast thou thus dealt with us? - Why hast thou given us all this trouble and anxiety, in going so far and returning with so much solicitude?
Thy father - Joseph was not the “real” father of Jesus, but he was “legally” so; and as the secret of his birth was not commonly known, he was called his father. Mary, in accordance with that usage, also called him so.
Sorrowing - Anxious, lest in the multitude he might not be found, or lest some accident might have happened to him.