12 As the sun was setting, Abram fell into a deep sleep, and a thick and dreadful darkness came over him. 13 Then the LORD said to him, "Know for certain that your descendants will be strangers in a country not their own, and they will be enslaved and mistreated four hundred years. 14 But I will punish the nation they serve as slaves, and afterward they will come out with great possessions. 15 You, however, will go to your fathers in peace and be buried at a good old age. 16 In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure."
17 When the sun had set and darkness had fallen, a smoking firepot with a blazing torch appeared and passed between the pieces. 18 On that day the LORD made a covenant with Abram and said, "To your descendants I give this land, from the river of Egypt to the great river, the Euphrates- 19 the land of the Kenites, Kenizzites, Kadmonites, 20 Hittites, Perizzites, Rephaites, 21 Amorites, Canaanites, Girgashites and Jebusites."
It is apparent from the text that the covenant and the visitation by the Lord came in a dream. During this entire sequence Abraham is in a deep sleep. It begins when he falls into a deep sleep as the sun sets and the dream continues without any indication that Abraham awoke.