In many South Indian marriages while the groom is tying the maṅgalasūtra to the bride, the priest usually chants the following verse.
Mangalyam tantunanena mama jeevana hetuna:
kanthe badhnami subhage twam jeeva sarada satam
It's meaning from this blog:
This is a sacred thread. This is essential for my long life. I tie this around your neck, O maiden having many auspicious attributes may you live happily for a hundred years.
Mangalyam thanthuna anena – This mangal sutra (This sacred thread) (thantu – thread)
hetuna – is essential (hetu – reason, purpose)
mama – my
jeevana – life (long life) (for my long life)
Kante – around your neck (in, on etc. prepositions are signified by the 'e' ending)
badhnami – I am tying
Subhage – oh, maiden of many auspicious attributes
twam – you (may you)
jeeva – live
sarada – years (from Sarad ritu)
satam – hundred
What's the origin of the verse? Which scripture contains this śloka?