Grammar - Beginner - Part 4
Neba naranai ねばならない
Predicative phrase (expressing obligation) meaning: have to, must.

1. After the stem of nai-form of verb

もう行かねばなりません。
Mou ikaneba narimasen.
I have to leave now.

若いうちはもっと仕事せねばなりません。
Wakai uchi wa motto shigoto seneba narimasen.
You must work harder while you are young.
(this uses the antiquated form se[neba] instead of the more common stem shi)

-> See also: nakereba naranai