Salam
A tradition of Hadrat Ubayy-bin-Ka`ab which is most probably based on the knowledge he received from the Holy Prophet, is the best commentary or this verse. He says:
"Allah gathered the whole of mankind and arranged it into separate groups according to their kinds or periods and gave them human shape and power of speech. Then He took a Covenant from them and made them witnesses concerning themselves and asked, `Am I not your Lord?' They answered, 'Most certainly, You alone are our Lord.' Then Allah said, `I ask the earth and the heavens and your father Adam to bear witness to this effect lest you should say on the Day of Resurrection that you had no knowledge of this. So note it well that none other than I is worthy of worship and that there is no other Lord than I. You should not set up any partner with Me. I will send to you My Messengers, who will remind you of this Covenant that you are Making with Me; I will also send My Book to you . At this the whole of mankind replied, "We bear witness to this: You alone are our Lord and our Deity: we have no other lord or deity than You."