Genesis 16:3 And Sarai Abram's wife took Hagar her maid the Egyptian, after Abram had dwelt ten years in the land of Canaan, and gave her to her husband Abram to be his wife.
And thus, they waited and waited and waited. Both of them were well into their retirement years when the initial promise was given, but they believed God anyway. Sarah was about 65 years old and Abraham was about 75 years, and they waited and waited. One year passes by, two years three years four years and nothing happens. Five years elapse, and still no child. Sarah is becoming a bit restless and nervous, for time is slipping away and nothing is happening.
Eight years, nine years, and then in desperation, in the tenth year she says you know what, the promise of God would never be fulfilled, and in that frame of mind she becomes ripe for plan B. Note carefully, in the following passages, the conclusion she has come to, and the subsequent logical substitute suggestion to her impatience. The same issue of impatience plagued the children of Israel over and over again, especially when they were encountering difficulties.
Genesis 16:2 And Sarai said unto Abram, Behold now, the Lord hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai. 4 And he went in unto Hagar, and she conceived: and when she saw that she had conceived, her mistress was despised in her eyes.
Genesis 16:5 And Sarai said unto Abram, My wrong be upon thee: I have given my maid into thy bosom; and when she saw that she had conceived, I was despised in her eyes: the Lord judge between me and thee.
May The Lord add His blessing to the study of His word. God bless!