Nedarim

R. Jeremiah asked R. Zera: If one separates of his own for his neighbour's [produce], to whom does the goodwill [value] belong?  Do we say, but for this man's produce, would the other's stack have been made fit to use?  Or perhaps, but for this man's stack, the other man's produce would not be terumah?  — He replied, Scripture saith, all the increase of thy seed … and thou shalt give. He objected: HE MAY SEPARATE HIS TERUMAH AND HIS TITHES WITH HIS CONSENT. Now if you say that the goodwill belongs to the owner, surely he [the maddir] benefits him? Hence this proves that the goodwill is his!  — I will tell you: it is not so. This means that the terumah belongs to the owner; 'HIS CONSENT also referring to the owner, who had announced, 'Whoever wishes to separate, let him do so.' Come and hear: R. Abbahu said in R. Johanan's name: He who sanctifies the animal must add the fifth, whilst only he for whom atonement is made sanctifies a substitute;  and he who gives terumah of his own for another man's produce, the goodwill is his. HE MAY TEACH HIM MIDRASH, HALACHOTH, AND AGGADOTH, BUT NOT SCRIPTURE. Why not Scripture — because he benefits him? But [by] Midrash too he benefits him? — Said Samuel: This refers to a place where the teaching of Scripture is remunerated, but not that of Midrash. How state this definitely?  —