What right did Yaakov have to use does devious methods for his personal gain?
Ramban #2: It is even possible that Lavan - who knew nothing about the novel method that Yaakov would ultimately employ - gave him the green light to use whichever method he saw fit.
Moshav Zekenim #2, Da'as Zekenim, Hadar Zekenim (to 30:38), Riva (to 30:32): Lavan cheated first. He was supposed to remove only young animals; he removed also adults. 3 The sticks were to compensate for this. "With the crooked, 4 you may be crooked" (Shmuel II 22:27). 5
Bechor Shor (to 30:33): It would be proper to leave the spotted animals in the flock, and the females could see them and give birth to such babies. Due to Lavan's adamancy, lest he claim "these spotted animals were born beforehand," they had to be removed. The sticks were to compensate for this. Yaakov stipulated to do so, and he did so openly.
Tosfos ha'Shalem (to 30:35 (3)), Radak (to 30:40): Yaakov used the sticks only on his own flock (what was born spotted, after they matured), lest they give birth to animals without the Simanim, and they will belong to Lavan. 6
Moshav Zekenim #1, Tosfos ha'Shalem (3): An angel told him to do so, 7 like it says below (31:10-12).
Moshav Zekenim #3: Yaakov intended to benefit Lavan 8 ! He prevented his own animals from mating with Lavan's lest the babies look like the fathers. And he covered Lavan's sheep to keep their wool clean. 9
Ohr Zaru'a (1:769): Yaakov used the sticks only on his own flock, and did not face Lavan's flock towards those with the appearances that Yaakov receives, lest Lavan say that they give birth to these appearances because they see such animals.
Malbim: Lavan should have left in the flock animals with white, so the female could see this and such animals would be born. Lavan removed everything with white, so the sticks were in place of this (something white for the females to see). 10
Oznayim la'Torah: To make up for the spotted and speckled sheep and goats that Lavan had removed from the flock. Refer to 30:35:3:1.
Gur Aryeh: Lavan had already shortchanged Yaakov by removing all the high-quality animals from the flock (refer to 30:36:2.2). Yaakov calculated that his loss far exceeded any possible gain by use of the sticks (at least by natural means).
Even though he did not cheat, since it looked unjust, Yaakov's children and their land were annihilated (Tosfos ha'Shalem 30:42 (1)).
Riva: He removed also Akudim, the healthy animals (and everything with white - Tosfos ha'Shalem 2) and the females (Tosfos ha'Shalem 4, citing Chatzi Menasheh, citing Riva of Orleans), and he changed the wages 100 times. Compare to Gur Aryeh, 30:37:1:12. Also refer to 30:32:1:2; 30:35:2:2.
Tosfos ha'Shalem (1): Yaakov took Livneh, Luz and Armon, to hint that he does so because Lavan is acting Naluz (crooked) and with Armimus (guile).
Tosfos ha'Shalem (to 30:33 (5)): This Heter is only for the same matter in which the other party cheated.
Riva: We say so to answer heretics; but it is not correct!
Tosfos ha'Shalem: Surely, had the angel not told him to do so, this would have no effect!
Ha'Kalir put "Meyachem b'Maklos b'Shikasos ha'Mayim" in the Piyut "Lema'an Tamim..." (the fourth Piyut that Ashkenazim say after finishing the Hakafos) on Hoshana Raba. Surely we do not request in the merit of trickery!
Tosfos ha'Shalem (2): Also, he caused Lavan to get animals born in summer, and Yaakov got those born in winter.
Ha'amek Davar: The Petzalos were like spots, and Machsof ha'Lavan was like blotches.
Why does it say that only the Livneh was moist?
Bechor Shor: Livneh is white only when it is moist. The others are white (under the bark) even when they are dry.
Gur Aryeh: They were all moist. The extra Vav in the word "v'Luz" connects it to the description above, "and [he also took a moist stick of] hazelnut...." 1
It seems that Gur Aryeh had the text in Rashi, 'a moist stick of hazelnut;' but we do not have this text. (EK)
What is Luz?
Rashi: It is a tree that makes small nuts.
Riva, Moshav Zekenim: It cannot be a tree that makes small nuts, for Bechoros 8a says that it bears fruits in 21 days! Rather, it is an almond 1 tree.
Riva supports this from a Midrash (and Yerushalmi Ta'anis 4:5), which says that almonds develop in 21 days.
QUESTIONS ON RASHI
Rashi writes: "'A stick of Livneh' - Livneh is the name of the type of tree." How might I have mis-understood it?
Gur Aryeh: I might have thought that 'Livneh' means 'white.' But the stick itself was not white; only by peeling it would the white underneath be revealed (and hence the name Livneh).