Genesis 30:40

40 Jacob separated those lambs from Laban’s flock. And at mating time he turned the flock to face Laban’s animals that were streaked or black. This is how he built his own flock instead of increasing Laban’s.

Genesis 30:40 Meaning and Commentary

Genesis 30:40

And Jacob did separate the lambs
The ringstraked, speckled, and spotted; and set the faces of the flocks,
that were all white, towards the ringstraked, and all the brown in the flock of Laban;
either to go before those that were all white, that they by looking at them might conceive and bring forth such, which was another artifice of Jacob's to increase his own sheep; or else he set at the water troughs the white sheep on one side of them, and on the opposite side the speckled ones that the same effect might also be produced the more successfully both by the rods and by the speckled lambs: and he put his own flocks by themselves, and put them not unto Laban's
cattle;
partly that they might not be mixed together, but kept distinct, that what was his property might be discerned from Laban's; and partly, lest his spotted ones, being mixed with Laban's white sheep, by continual looking at them, should conceive and bring forth such likewise, and so his flocks be lessened.

Genesis 30:40 In-Context

38 Then he placed these peeled branches in the watering troughs where the flocks came to drink, for that was where they mated.

39 And when they mated in front of the white-streaked branches, they gave birth to young that were streaked, speckled, and spotted.

40 Jacob separated those lambs from Laban’s flock. And at mating time he turned the flock to face Laban’s animals that were streaked or black. This is how he built his own flock instead of increasing Laban’s.

41 Whenever the stronger females were ready to mate, Jacob would place the peeled branches in the watering troughs in front of them. Then they would mate in front of the branches.

42 But he didn’t do this with the weaker ones, so the weaker lambs belonged to Laban, and the stronger ones were Jacob’s.