The Covenant Making God, Genesis 15

The last 15 verses of Genesis 15 focus on God's promises of land to Abram in 3 ways: the specific location, God's prophesy about Abram's descendants coming into the land after 400 years of slavery, and most importantly the "covenant ratification ceremony." The curious thing about the ceremony is that both parties involved in the covenant were supposed to walk down a path together to signify that they were pledging their lives to their agreement. But God puts Abram to sleep. So, who walks down the path and what does that signify, for Abram and for us? There is some deep theology there if we're willing to think through it.