Comentario sobre Levítico 15:3

רר [WHETHER HIS FLESH] DRIP — This word is connected with ריר "spittle" — the meaning is that his flesh runs with its issue as spittle, i. e. that it (the flow) comes forth clear in appearance (not thick and troubled).

טומאתו בזובו, his impurity in his issue, etc. According to Torat Kohanim the sequence of these words mean that only the whitish coloured discharge transmits impurity as distinct from a reddish, blood-coloured discharge. The meaning is that but for the restrictive letter ב in the word בזובו, a discharge of blood would have been considered as conferring impurity even if the Torah had written the word זובו טמא הוא as it did in verse 2, we would have had to rule that a discharge of blood is also conferring ritual impurity. In other words, the restrictive expression we discussed at length in verse 2 would not have sufficed. The reason would have been that the expression זובו was used by the Torah in both verses. We would have been forced to conclude that the restrictive nature of the word זובו referred only to the afflicted person himself and not to his discharge. I would then have learned the קל וחומר from the הלכה that his spittle confers impurity as we explained on verse 2. Alternatively, we would have reasoned that the reason we have to exclude it is only because there was a special letter needed (the letter ו in the word וזאת) to include urine otherwise we would have excluded it.

רר בשרו את זובו, the word is similar to the expression ויורד רירו על זקנו “his spittle ran down his beard” in Samuel I 21,14 when David pretended to be mentally disturbed in order to save his life. The flesh of the person afflicted drips with this discharge.