Learn Farsi: ما به سمت کوه نرفتیم مبادا در یخ گیر کنیم. - We did not go towards the mountain lest we get stuck in the ice.

It follows the conjunction mabâdâ (lest / so that not). Because mabâdâ introduces a hypothetical, uncertain outcome that the speaker wants to prevent, it requires the verb to be in the present subjunctive tense.

Since mabâdâ means "so that not", why isn't the verb negative (gir nakonim)?

The word mabâdâ already contains the negative meaning built right in. Because the negativity is carried by the conjunction, the verb that follows it stays affirmative (gir konim). Adding a negative prefix to the verb would create a confusing double negative.

Where is the usual be- prefix for the subjunctive verb gir konim?

gir kardan (to get stuck) is a compound verb. In modern Farsi, the be- prefix is almost always dropped when forming the subjunctive of a compound verb using kardan, because the first part of the verb (gir) already holds the focus.

How does the phrase be samt-e work to mean "towards"?

The word samt means "direction" or "side". When paired with the preposition be (to) and connected to kuh (mountain) using the invisible linking vowel called ezafe, the phrase be samt-e kuh literally translates to "to the direction of the mountain".