[2:129] Our Lord! And send among them a messenger, one of them, who shall recite to them Your signs, and teach them the Book and Wisdom, and purify them; You are the Mighty, the Wise.
Because the obligations were received from messengers and were not merely something intellectually perceived, [Abraham] asked that they not be left to themselves, without a messenger or law. He requested that the messenger be one of them so that they would feel more at home with him and it would be easier for them. Its meaning, rightly understood, is that when He (s) informed [Abraham] of the state of our Prophet (ṣ), [Abraham] asked for the completion of what He had promised by way of the one He commanded.