Today Hebrew grammar is well understood and there are many books on it. Rashi, however, lived before the age of grammar books. A major Rashi method is therefore the teaching of basic grammar.

Many students belittle this aspect of Rashi. They erroneously think that because of modern methods we know more. However Rashi will frequently focus on rare grammatical points not covered in conventional textbooks.

There are many classical aspects to grammar whether in Hebrew or other languages. They include
• The rules for conjugating verbs. These rules govern how you differentiate person, plurality, tense, mode, gender, mood, and designation of the objects and indirect objects of the verb. For example how do you conjugate, in any language, I sang, we will sing, we wish to sing, she sang it.
• Rules of agreement. For example agreement of subject and verb, of noun and adjective; whether agreement in gender or plurality.
• Rules of Pronoun reference.
• Rules of word sequence. This is a beautiful topic which is not always covered in classical grammatical textbooks.

Today we cover the beautiful rule of one letter, prefix, prepositional connectives. Hebrew has several one-letter prefix prepositional connectives such as Beth which means in, Lamed which means to, Mem which means from etc. The Radack following other Hebrew grammarians explains the novelty that each of the one letter prefixes can assume the meaning of any other of the prefixes. Indeed, Lamed can mean to but can also mean from. Using this principle we can explain the poetic verse Nu21-29d:
• Woe to you Moab, you are lost, nation of [god] Kemosh:
  • You must give your sons to fleers [from] and
  • --- ---- ---- ---- daughters in captivity to
• the Emorite Kingdom [in] Sichon.

I believe Rashi's main point is that the one-letter lamed prefix simultaneously means from and to. That is the verse puns the Lamed to indicate the double tragedy that the males are fleeing from while the femals are (helplessly) given in capitity to the Emorite Kingdom. In fact there is a further pun here. The one-letter prefix lamed can also mean for the sake of. So the verse is cynically saying: The men are fleeing for the sake of the Emorites who want the women for themselves!