Genesis 15

The Lord comes to Abram in a vision and tells him:

• You will have an heir, despite your barren wife.  Abram is worried a servant will get all his stuff.
• Your descendants will be many
• Said descendants will have a crappy time of it for a little while (400 years!!!)

Abram then kills some stuff for the Lord, and the Lord does a bit of hocus pocus before telling him about all the peoples his great-great-grandkids will have to kill to get the good life.