A literal translation of the given phrase would not convey the meaning of it. There are a few different translations depending upon the circumstances. The one given above has the general meaning "May God protect you". "Dia leat" meaning "God be with you" is the farewell given to the person who is leaving. A third possibility based upon a saying quoted in Dinneen's Irish-English dictionary is "Do chumhdach ar Dhia" meaning "God is your protection".