«بِالرَّفَاءِ وَالْبَنِينَ»
May there be harmony and children, a traditional expression of congratulation.
Within a wedding setting this conventional expression implies the occasion itself, such as aʿrasta, “you have married,” without explicitly naming it. The customary pairing of the words and the marriage occasion supplies the missing situational meaning.
Association by convention is therefore one clue to ellipsis. Its force depends on actual usage and setting rather than on the isolated words alone.