And all four of these words and prefixes teach about permission, not about obligation, except for the fifth prefix – the ה which accompanies the infinitive – it will come in one of three ways:

1. Sometimes it indicates the persistence of time, like בבואם אל אוהל מועד (when they go into the tent of meeting)²¹⁸.

footnotes: ²¹⁸ Exodus 30:20.

2. To instruct about the frequency - בבואכם אל הארץ (when you come into the land)²¹⁹.

footnotes: ²¹⁹ Numbers 15:18.

If the action of the circumstance is a necessity, whether from nature or from an obligation in the Torah.

There is probably a typographical error here. The Malbim clearly meant the the prefix letter ב or כ, not the prefix letter ה. See Rule 97.