Genesis 30:40

38He set the rods which he had peeled opposite the flocks in the watering troughs where the flocks came to drink. They conceived when they came to drink.

39The flocks conceived before the rods, and the flocks produced streaked, speckled, and spotted.

40Jacob separated the lambs, and set the faces of the flocks toward the streaked and all the black in Laban’s flock. He put his own droves apart, and didn’t put them into Laban’s flock.

41Whenever the stronger of the flock conceived, Jacob laid the rods in front of the eyes of the flock in the watering troughs, that they might conceive among the rods;

42but when the flock were feeble, he didn’t put them in. So the feebler were Laban’s, and the stronger Jacob’s.