Commento su Genesi 30:37

מקל לבנה STICKS OF לבנה — a tree that is called לבנה — just as you say (Hosea 4:13) “Under oaks and poplars (ולבנה)” I think it is what is called in old French tremble; English trembling-poplar, which is white.

AND JACOB TOOK HIM STICKS OF POPLAR. As soon as they agreed that his hire would be these colors it was permissible for Jacob to do whatever he could to cause them to give birth in this manner. Perhaps Jacob had made a condition that he may do with them whatever he wants since Laban did not know of the ramifications of this measure, nor did Laban’s shepherds sense anything when they saw the sticks in the gutters once a year during the days of Nisan. For When the flocks were feeble¹⁶⁵Verse 42 here. in the days of Tishri, he did not put them in, otherwise not a hoof would have remained for Laban.
Now some commentators¹⁶⁶R’dak. say that the first year [Jacob did not make use of these sticks, but] there were born to him many speckled and spotted ones by virtue of G-d’s blessing which the angel showed him.¹⁶⁷Further, 31:12. And then he put the sticks in front of those which were his so that they should give birth in their form. This would prevent Laban from saying that their offspring was stolen by Jacob, [as he would have claimed had they given birth to other colored offspring].
This is the meaning of whensoever the stronger flocks became heated,¹⁶⁸Verse 41 here. referring to those that had been born to Jacob by way of G-d’s blessing; but when the flocks of Laban were feeble, he put them not in; so that the feebler were Laban’s, for they did not give birth to speckled ones, and the stronger were all Jacob’s,¹⁶⁵Verse 42 here. including their offspring, for they gave birth to speckled ones.

מקל לבנה, the reason why the letter ק in the word מקל has the vowel patach instead of the vowel tzeyreh, as we might have expected, is because it is in a construct form to the word לבנה, the tree that this staff was cut from. We encounter a similar construction for the same reason in Leviticus 27,32 where the Torah speaks of Ma-assar bakar instead of ma-asser bakar, “tithe of the cattle.” The word מעשר is in a construct form to the word בקר. We find a similar construction in Jeremiah 6,26 with the expressionמספד תמרורים, as well as in Amos 5,16 and Numbers 18,26 and Numbers 22,27.