Nba! A ni ce, Maggie 
Good question – thanks for posting it in the Forum!
The possibilities are endess, but here’s some basic ones that come to mind and that I frequently hear/use in marriage contexts (I’m writing them out in full instead of contracting the k’à or k’u, etc):
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Ala ka à kɛ furu ye
‘May God make it a wedding’ -
Ala ka u kanw bɛn
‘May God unite their voices’ -
Ala ka sen ni bolo bɔ à la
‘May God make feet and arms come out of it’
(as in, ‘May God bring them children’)