Genesis 30:36

And he set three days' journey between himself and Jacob,.... Not three days' journey for a man, but for cattle; this distance there was between the place where Laban and his sons kept the spotted, speckled, and brown cattle, and that in which Jacob kept the flock only consisting of white sheep; and this was done, that the flocks might not be mixed, and that there might be no opportunity to take any of the spotted ones, and that they might not stray into Jacob's flock; or lest any of his seeing them might bring forth the like, such precaution was used:

and Jacob fed the rest of Laban's flock; those that remained after the spotted, speckled, and brown were taken out; and Jacob having none but white sheep, there was no great likelihood, according to the course of nature, of his having much for his hire; since he was only to have the spotted, speckled, and brown ones that came from them, and generally like begets like; and, according to the Jewish writers p, those that were committed to his care were old and barren, and sick, and infirm, that so he might have no profit from them.

p Bereshit Rabba, sect. 73. fol. 64. 1. Targum Jon. Jarchi in loc.