Most people are aware that Hebrew verbs come from three-letter roots. Each root is conjugated in the 8 dimensions of person, gender,plurality, tense, activity, modality, direct-object, and prepositional connective. For example the root Shin Mem Resh means to watch. The conjugations Shin-Mem-Resh-Tauv-Yud and Nun-Shin-Mem-Resh-Nun-Vav mean I watched and we were watched respectively.

The rules for Hebrew grammar are carefully described in many modern books and are well known. Rashi will sometimes comment when a verse is using a rare conjugation of an odd grammatical form.

When presenting grammatical Rashis my favorite reference is the appendix in volume 5 of the Ibn Shoshan dictionary. This very short appendix lists most conjugations.

One of the challenges of learning Hebrew grammar is understanding the meaning or meanings associated with the various conjugational modes. There are four approaches to interpreting the Hebrew hitpael grammatical mode. Rashi's approach to the hitpael is that it means interactive. Hence the hitpael form of the root Gimel-Lamed-Lamed, to roll, would mean to interactively roll [accusations] on us. Using this grammatical translation Rashi translates Gn43-18d as follows: And the men were afraid, because they were brought into Joseph’s house; and they said, We are brought in because of the money that was returned in our sacks at the first time; that he may seek to interactively roll accusations on us and fall upon us, and take us for slaves, and our asses. Here the connotation is to pick on someone, to find fault with them, and to interactively use everything they say against them.