In Genesis 21 the Lord fulfills his promise to provide Abraham and Sarah with a son. Throughout the chapter we learn three reasons why joy is found in taking God at his word.

Resources:

Genesis 21:1-34
New American Commentary (Genesis) by Kenneth Mathews
ESV Study Bible, Genesis Notes
Preach the Word (Genesis) by Kent Hughes
Cost of Discipleship Part 3 (Sermon) by Ray Ortlund at Immanuel Nashville