No sooner had Hagar's union with Abraham been consummated, and she felt that she was with child, than she began to treat her former mistress contemptuously, though Sarah was particularly tender toward her in the state in which she was. When noble matrons came to see Sarah, she was in the habit of urging them to pay a visit to "poor Hagar," too. The dames would comply with her suggestion, but Hagar would use the opportunity to disparage Sarah. "My lady Sarah," she would say, "is not inwardly what she appears to be outwardly. She makes the impression of a righteous, pious woman, but she is not, for if she were, how could her childlessness be explained after so many years of marriage, while I became pregnant at once?"
Hagar Among the Fathers
Legends of the Jews 5:128