Genesis 16:4

And he went in unto Hagar, and she conceived; and when she saw that she had conceived, her mistress was despised in her eyes. The plan of Sarai to which Abram had consented was decidedly human and did not have the divine approval. Hagar having conceived, her mistress was looked down upon in her eyes. The Jews, like the Orientals in general, regarded barrenness as a great evil and a divine punishment, Leviticus 20:20, and fruitfulness as a great good and a divine blessing, Exodus 23:26; Deuteronomy 7:14. Still, the attitude of Hagar was a presumption, since she was not Abram's second wife, but retained her subordinate position throughout.