Because God wanted the unchanging nature of his purpose to be made very clear to the heirs of what was promised, he confirmed it with an oath.
Mudzimu o vha a tshi ṱoḓa u sumbedza tshoṱhe vhe a vha fulufhedzisa ifa ḽawe uri Ene ha litshi u ita zwe a dzula o vhofha, ndi zwe a tou khwaṱhisa na nga muano.