There are perfect tense verbs and imperfect tense verbs. And it is possible to determine with many verbs whether they are perfect or imperfect. And with many commandments, the Torah reveals that a verb is in imperfect tense by repeating the infinitive with the verb, like עזב תעזב, הקם הקים, שלח תשלח – so it means that it will be an imperfect tense verb, which can even be done several times (as will be explained later in rule 38).

And with many commandments, we can know through logic that it is an imperfect tense verb likeאם כסף תלוה (If you lend money)³⁶, וכתבתם על מזוזות (And you shall write them upon the door-posts)³⁷. And when it is written וכסהו (and cover it with dust)³⁸, it is in perfect tense and it means that it is sufficient to cover it only one time. And this is why it is written וכסהו and not ויכסהו (because of rule 44 that is explained later). And when it is written וכסהו with a pronoun, it is clarified later in rule 151.

Unlike most modern languages, verbs in the Biblical Hebrew have only two tenses, perfect and imperfect. Perfect tense is used to express a completed action, while imperfect tense is used to express an incomplete action.

footnotes: ³⁶ Exodus 22:24. ³⁷ Deuteronomy 11:20. ³⁸ Leviticus 17:13.