Good middot make good neighbors

From todays Daf Yomi (which you can read in the Rif here and here), Bava Batra 5a.

[One] Ronya had a field which was enclosed on all four sides by fields of Rabina. The latter [fenced them and] said to him: pay me [towards] what I have spent for fencing. He refused to do so. Then pay [towards] the cost of a cheap fence of sticks. He again refused. Then pay me the hire of a watchman. He still refused. One day Rabina saw Ronya gathering dates, and he said to his metayer: Go and snatch a cluster of dates from him. He went to take them, but Ronya shouted at him, whereupon Rabina said: You show by this that you are glad of the fence. If it is only goats [you are afraid of], does not your field need guarding? He replied: A goat can be driven off with a shout. But, he said, don't you require a man to shout at it? He appealed to Raba, who said to him: Go and accept his last offer, and if not, I will give judgment against you according to R. Huna's interpretation of the ruling of R. Jose.

Ronya bought a field adjoining a field of Rabina. The latter thought he was entitled to eject him in virtue of his right of preemption. Said R. Safra the son of R. Yeba to Rabina: You know the saying, The hide costs four zuzim, and four are for the tanner.

What is the meaning of this common saying, "the hide costs four zuzim, and the tanner costs four zuzim"?

Before attempting to answer that, I would just pass judgement on the first incident. (I know -- who is this nobody that seeks to pass judgement on an Amora, but still I will say what my reaction to this is.) While in terms of the dictates of the law, Ravina is in the right, he still strikes my 21st century Western sensibilities as somewhat of a bully. It feels unjust, as he did not ask for the fence, and it was constructed somewhat against his will only because Ravina entirely encompassed him. And Ravina resorted to a sort of trick to extract this "admission" -- by sending someone to snatch dates. Who says that thieves, or goats, are prevalent. And even if prevalent, perhaps Ronia would not have gone to the trouble of building a fence, and would absorb the damage; but if he sees someone about to steal, why shouldn't he shout to keep the person away. Still, it is nicha leih, but it feels unjust; and indeed, when dealing with money matters, often people conduct themselves in ways they might not were their own money not at stake. So Ravina might be right, but I am pretty certain that Ronia deeply resented him for this.

In the second incident, Ravina sought to eject Ronia by virtue of his right of preemption, again because he owned the field. Some may try to explain the application of this popular saying, which is cryptic to us, as a halachic judgement. See for example Nimukei Yosef. Since בר מצרא is a takkana, and since Ronia was poor, כוון דדינא דבר מצרא אינו [ב״מ לף קח.] אלא משוס ועשית הישר והטוב אין ישר וטוב גדול מזה הלכך לא מפקינן מידו. And there is another explanation there, of this cryptic statement. (Regardless, Rif does not bring this story down lehalacha, so maybe one should not identify halachic reasons for this, which might then be used to pasken in other cases.)

I would attempt the following explanation. The gemara did not state that he thought he was entitled to eject him, but rather that he thought to eject him. So Rav Safra's statement might not be a reason why Ravina is not entitled, but rather a reason not to do it nonetheless. We saw earlier that good fences do not necessarily make good neighbors, because the cost of the fence became a point of contention between them.

The same here. Ravina was absolutely entitled to eject him. But Ronia was a local farmer, and had at least one other field which was adjacent to Ravina's.

When you say "the hide costs four zuzim, and the tanner costs four zuzim", the meaning is as follows. You calculate the cost of buying a hide, and think it is a good deal, at four zuz. But you need to also factor in the costs which will accrue related to this initial purchase. Your four-zuz hide really ended up costing you double what you reckoned, because you have to pay the tanner!

Good fences don't make good neighbors. Good middot make good neighbors. And sometimes that means not pressing your rights to your full advantage, when it causes others to suffer a loss. Ronia would not be happy being ejected from his newly bought field, with all his work in purchasing it now done in vain. Ravina would be entirely in the right, but he would make an enemy out of his neighbor, Ronia. And since Ronia was a local farmer who owned other fields, Ravina would likely have to deal with him in the future. Maintaining cordial relations in this regard was essential. And this was Rav Safra's mussar, and practical life- and business- advice.

Indeed, if Ravina set this precedent of bar mitzra, the next time Ravina sought to buy a field, his newly made resentful enemy might try to use bar mitzra to foil his business plans.