Right after the LORD has make a covenant with Abram, showing him that the foundation of this covenant is God’s character, we see how this covenant works in a practical way.
When making his covenant with Abram (Genesis 15), our LORD showed him that His holiness (represented by the furnace) and his guidance (represented by the torch) are the foundation for this formal relationship with Him. The main piece of this covenant is Abram’s seed.
In chapter 16 we see how Abram and Sarai attempt to rationalized God’s promises, concluding that the fulfillment of such a promise must require their ‘help’. What follows is not only a good example of human actions that reflect our heart’s condition, but also exemplifies how, despise of His people’s failure, God keeps his promise of blessing Abram’s seed (because He is holy), and rescues Hagar, guiding her out of the wilderness (remember the torch).