I’m going to start pretty far afield, with the offerings that were brought at the dedication of the Mishkan:
The Midrash goes into great detail about the symbolism of each of these items. Rashi goes through a few of them. Here is what he says about the עולות:
We know the incident with אברהם, when he served the three angels. We certainly know the incident with יצחק, the עקדה. But what does יעקב have to do with sheep?
Honesty in business dealings is called אמונה, faith. Dishonesty is not only a sin against man, it is a sin against G-d, saying “I don’t trust Your judgement about what I deserve”. The Gemara says that the first question one is asked in עולם הבא is about honesty in business:
If Yaakov is so honest, what’s with the sticks? One approach is to call the whole thing an incomprehensible miracle:
The Zohar then goes on to describe the kabbalistic implications of Jacob’s
branches in terms of the sephirot and mystical implications. But I won’t take that approach, for two reasons: first, I don’t understand it. Second, it belies the idea of Jacob’s honesty in his dealings with Lavan, if he is using tricks that Lavan couldn’t know about. Even if practical kabbalah is not forbidden magic, it clearly goes against the spirit of their agreement.
The simplest explanation, the one that most commentators assume, is that the peeled white stripes somehow made the sheep give birth to white-speckled lambs.
Rashi translates (based on Chabad’s translation of his Old French) לבנה ולוז וערמון as poplar, hazelnut and chestnut, and says:
Dr. William Etkin, who was a professor of anatomy at the Albert Einstein School of Medicine and a friend of my grandfather, wrote an article in Tradition (Fall 1965) about the question of “Jacob’s Cattle and Modern Genetics”. The idea of the maternal environment affecting the genotype and hence the phenotype of the offspring is inconsistent with what we know about how genes work (there is a concept of epigentic inheritance but just the sight of striped rods couldn’t affect the offspring). Etkin proposes that Jacob (with his years of sheep-breeding experience) knew the rods wouldn’t affect anything. He was relying on G-d’s providence to allow him to earn a living:
Note that in the description of the sheep-breeding, there is no mention of the sticks. It’s straight genetics: speckled males crossed with solid females have speckled offspring.
The rods were there to keep Lavan from accusing him of stealing. Jacob would put the rods in the water and the sheep would breed and multiply naturally, and some of the all-black sheep would have speckled children. If “speckling” is a recessive gene, then about a quarter of the offspring would express it. If Lavan didn’t have Jacob’s knowledge of sheep genetics and wanted to draw conclusions about the rods, then he was free to do so.
This is, I think, the idea behind the Gemara’s description of Jacob’s duplicity: he is honest but would allow others, who see only dishonesty, to fool themselves:
But I still think that’s too devious for a paragon of honesty. I agree that the placement of the rods had to be in the open, and I don’t think it reflects badly on Jacob to assume he really thought the sight of the rods would affect the children. He was being honest and ה׳ helped him succeed. Nonetheless, I would propose there was a mechanism for the rods to actually work that is consistent with our understanding of physiology.
The actual description of what Jacob did doesn’t say anything about the sheep seeing the rods; they were just put in the water. It also doesn’t say anything about the rods causing the offspring to be speckled. It says ויחמנה בבאן לשתות. What does ויחמנה mean?
I would read this story as Jacob, as an experienced sheep-breeder, using an herbal fertility drug on the sheep. I don’t know what poplar, chestnut and hazel in the drinking water would do to sheep, but it’s not unreasonable that they could affect the ewes. It’s the suggestion that it affects the genetic makeup of the offspring that’s incompatible with how we understand genetics. The sheep would give birth to lambs, some of which could be speckled, and he could breed those with the stronger, “early-breeding” sheep to increase the value of his flocks.
It’s all above-board, completely honest and reasonable, and serves as an object lesson in the balance of hishtadlut and bitachon. Jacob does what is necessary to earn a living, all with the best science available to him (as we discussed in the past, whether or not the rods actually work is irrelevant; it’s the attitude that matters). He stays honest, never stealing or even doing anything suspicious, trusting that ה׳ will reward him appropriately. And ה׳ does; the sheep are miraculously manipulated to make him fabulously wealthy.