Principal English Translation:
thus it shall be (see attestations)
See also ma ihui.
Attestations from sources in English:
ma yuh muchiua = May it be done (Amen).
Fray Alonso de Molina, 1546 (Códice Franciscano, 35–6); translation by Mark Z. Christensen, "Nahua and Maya Catholicisms: Ecclesiastical Texts and Local Religion in Colonial Central Mexico and Yucatan," Ph.D. Dissertation, Pennsylvania State University, 2010, Appendix B, 2.
ma i mochihua, ma iuhqui mochihua = let it be done (equivalent to "Amen" and often seen in testaments)
Rebecca Horn's notes from Nahuatl classes with James Lockhart, currently being harvested for this dictionary by Stephanie Wood.
Attestations from sources in Spanish:
ma yuh ye in amoyollo = estad seguros de ello
Rémi Siméon, Diccionario de la lengua náhuatl o mexicana (Mexico: Siglo XXI, 1988), 241.