God cannot lie and when he makes a promise we can rest assured by his character that it will come to pass. His promise to Abraham was that his children would be as many as the stars in the sky or as the sand upon the seashore. (Genesis 22:17) How would this be true when Abraham was old and Sarah had passed childbearing years? Abraham considered his body to be near death and the womb of Sarah now dead. (Romans 4:19)
Sarah doubted and caused Abraham to deviate from God’s plan in having a child with their maid. (Genesis 16:2) Sarah thought at least then they could ensure that God’s promise would come to pass. This was not the case and the maid became resentful of Sarah and caused her more distress.
God’s faithfulness is not dependent on our actions and even when we make mistakes, he will keep his promise to us. Abraham had a relationship with God and because he listened and obeyed, God instructed him to send away his firstborn son with the maid. (Genesis 21:12) Although they made a mistake, God still kept his promise in their old age. (Genesis 24)
The requirement for God’s promises to be fulfilled is to listen and obey and trust in his word. It maybe even years before we see the manifestation of things promised. It pays to wait on God and trust that what he said will come to pass. “For still the vision awaits its appointed time; it hastens to the end—it will not lie. If it seems slow, wait for it; it will surely come; it will not delay.” (Habakkuk 2:3)