Luke wrote this book to a man named Theophilus. Some translations follow their own culture's way of addressing a letter and write "Dear Theophilus" at the beginning of the sentence. Theophilus means "friend of God" (See: [[rc://en/ta/man/translate/translate-names]])
This refers to Jesus' ascension into heaven. AT: "until the day on which God took him up to heaven" or "until the day that he ascended into heaven" (See: [[rc://en/ta/man/translate/figs-activepassive]])