Genesis 30:37-39

30:37 But Jacob took fresh-cut branches from poplar, almond, and plane trees. He made white streaks by peeling them, making the white inner wood in the branches visible. 30:38 Then he set up the peeled branches in all the watering troughs where the flocks came to drink. He set up the branches in front of the flocks when they were in heat and came to drink. ¹  30:39 When the sheep mated ²  in front of the branches, they ³  gave birth to young that were streaked or speckled or spotted.

[30:38]  ¹ sn He put the branches in front of the flocks…when they came to drink. It was generally believed that placing such “visual aids” before the animals as they were mating, it was possible to influence the appearance of their offspring. E. A. Speiser notes that “Jacob finds a way to outwit his father-in-law, through prenatal conditioning of the flock by visual aids – in conformance with universal folk beliefs” (Genesis [AB], 238). Nevertheless, in spite of Jacob’s efforts at animal husbandry, he still attributes the resulting success to God (see 31:5).

[30:39]  ² tn The Hebrew verb used here can mean “to be in heat” (see v. 38) or “to mate; to conceive; to become pregnant.” The latter nuance makes better sense in this verse, for the next clause describes them giving birth.

[30:39]  ³ tn Heb “the sheep.” The noun has been replaced by the pronoun (“they”) in the translation for stylistic reasons.