Genesis 30:40
And Jacob did separate the lambs, and set the faces of the flocks toward the ringstraked, and all the brown in the flock of Laban; and he put his own flocks by themselves, and put them not unto Laban’s cattle. And Jacob did separate the lambs, and set the faces of the flocks toward the ringstraked, and all the brown in the flock of Laban; and he put his own flocks by themselves, and put them not unto Laban’s cattle.
Genesis 30:40 belongs to the account of Jacob's stay and labor in Laban's household and his departure for Palestine. In that account Jacob personally separated, managed, and tended his own flocks apart from Laban's cattle. That period shows God's care for Jacob despite his selfishness and unfaithfulness.
The verse shows God blessing Jacob's labor in Laban's household with abundant flocks and herds. God prospered Jacob in his flocks and herds despite Laban's efforts to deprive him of his right. It is part of the checkered and unsatisfactory experiences of Esau and Jacob. Those experiences show Jacob's selfish plottings and his consequent suffering, where Jacob overreached and supplanted others and himself met overreaching. God's providence, though seeming slow, brings retribution sooner or later.
Jacob as a herdsman personally caring for, separating, and managing flocks defines necessary work on the Sabbath. Feeding, watering, milking, and other chores required for the life and welfare of people and stock must be performed on the Sabbath the same as on any day. Such work is always to be reduced to a practical, merciful minimum.