The second of the great “O” antiphons has the incipit O Adonai and is the antiphon indicated to be sung with the Magnificat at second Vespers on 18 December. In comparison with the first antiphon O Sapientia we see that both antiphons use the same chant melody in Mode II. This text pictures the Messiah as the Lord of Israel who judges and decides with equity and “shall strike the earth with the rod of his mouth”.
O Adonai, et Dux domus Israel, qui Moysi in igne flammae rubi apparuisti, et ei in Sina legem dedisti: veni ad redimendum nos in brachio extento
(O Adonai [Lord], and leader of the House of Israel, who appeared to Moses in the fire of the burning bushand gave him the law on Sinai: Come and redeem us with an outstretched arm)