「Commands, Requests, Suggestions, Approval, Disapproval, Prohibition, and Obligation」
The stem of the masu form of a verb, followed by nasai, expresses a command. This pattern is mainly used by teachers and parents when speaking to their students or children. Nasai is the imperative form of the honorific verb nasaru ("do") and is used here as an auxiliary verb.
Samui kara kore o kinasai.
Wear this, since it is cold.
Neru mae ni ha o migakinasai.
Brush your teeth before you go to bed.
Mō ichido kono ka o fukushū shinasai.
Review this lesson once more.
Hope this helps!
°˖ ✧◝(○ ヮ ○)◜✧˖ °こゆうきあいはら°˖ ✧◝(○ ヮ ○)◜✧˖ °