John Gills Exposition of the Bible Commentary - Genesis 15:17
And it came to pass, when the sun went down ,.... It was going down when the deep sleep fell on Abram, and now it was quite gone or set: and it was dark ; which is not always the case as soon as the sun is set, there is a twilight for a while, and if a clear night the stars appear; but, as Aben Ezra observes, this was a dark and cloudy night; so it was a dark night, a time of great affliction and distress to the posterity of Abram, when their sun was set, or after the death of Joseph: ... read more
Matthew Henry's Complete Commentary - Genesis 15:17-21
Here is, I. The covenant ratified (Gen. 15:17); the sign which Abram desired was given, at length, when the sun had gone down, so that it was dark; for that was a dark dispensation. 1. The smoking furnace signified the affliction of his seed in Egypt. They were there in the iron furnace (Deut. 4:20), the furnace of affliction (Isa. 48:10), labouring in the very fire. They were there in the smoke, their eyes darkened, that they could not see to the end of their troubles, and themselves at a... read more