Moses
Genesis 16:4ESV·traditional attribution

And he went in to Hagar, and she conceived. And when she saw that she had conceived, she looked with contempt on her mistress.

John Calvin Reformed @genevareformer

4. Her mistress was despised in her eyes . Here Moses relates that the punishment of excessive precipitancy quickly followed. The chief blame, indeed, rested with Sarai; yet because Abram had proved himself too credulous, God chastises both as they deserve.

Matthew Henry Presbyterian @wholebiblehenry

We have here the immediate bad consequences of Abram's unhappy marriage to Hagar. A great deal of mischief it made quickly. When we do not well both sin and trouble lie at the door; and we may thank ourselves for the guilt and grief that follow us when we go out of the way of our duty. See it in this story. I.

Commenting on Genesis 16:4-6

John Gill Reformed Baptist @doctorgill

And he went in unto Hagar, and she conceived,.... The formality of the marriage being over, he enjoyed her as his wife, and she immediately conceived by him: and when she saw that she had conceived; when she perceived that she was with child: her mistress was despised in her eyes; she thought herself above her, and treated her as her inferior, with contempt, and...