Midrasz do Przysłów 4:15

(Fol. 21) Raba said: "Whence is it intimated in the Torah concerning incest of secondary degrees? (forbidden by Rabbinical enactment). It is said (Lev. 18, 27) For all those gross abominations (ha-ail) have the men of the land done, who were before you; i.e., ha-ail (gross), hence there must also be minor ones. This refers then to incest of secondary degrees. Whence do we know that the word ail refers to something great? It is written (Ez. 17, 13) But the mighty (ai-lay) of the land did he take away." Shall we assume that this is in contradiction to the opinion of R. Levi? for R. Levi said: "The punishment for fraudulent measures is severer than that for incest, for the former, Scripture terms (Lev. 18, 24) Ail, while the latter it terms (Deut. 25, 16) aile." Of course, ail is strong; however, aile is still stronger. But concerning incest it is also written (Lev. 18, 29) aile? This is to exempt fraud measures from Kareth. If so, then in what respect are fraudulent measures severer than incest? In the following: For the crime of incest one is able to offer repentance, but for the crime of fraudulent measures one cannot repent, [because he does not know whom he has cheated] R. Huna said: "We infer [this prohibition concerning incest of secondary degree] from the following, (Ecc. 12, 9) Yea, he pondered and sought out, and set in order many proverbs." Ulla, in the name of R. Elazar, explained it: "Prior to the time of Solomon, the Torah was like a basket without handles, [that could not have been grasped,] but when Solomon came he attached the necessary handles." R. Oshia said: "We infer [the above] from the following (Pr. A, 15) Avoid it, pass not through by it, turn off from it and pass away." R. Ashi said: "Unto what could that of R. Oshia's explanation be likened? Unto a frail man watching a garden; if he watches it from the exterior, the interior is also protected; but if he watches it only from the interior, the exterior is left unprotected." Nevertheless R. Ashi's analogy is false, for there [if one watches from inside of the garden] protection at least is afforded for within, but here if one does not safeguard himself against the incest of secondary degrees he may reach the violation of even a real Ervah. R. Cahana said: "We infer the above from the following (Lev. 18, 30) Therefore shall ye guard My guard; i.e., make a guard which may protect, (enact measures to prevent a transgression of the Biblical law)" "If so," said Abayi to R. Joseph, "then this is Biblical." "Yea, it is Biblical, but it has been explained by the Rabbis." "But the entire law is thus explained by the Rabbis, and why call only this Rabbinical?" We must therefore say that it is catually a Rabbinical law, and the Bible text (quoted) is a mere intimation.