Why does the narrator repeat the words, "Never shall I forget," on page 32?

The narrator repeats these words for emphasis..... the reader needs to understand the seriousness and the truth of Elie's words.

Elie weasel used the repetition to make himself not forget the horrible experiences he saw in the past. This, he uses a repetition so he can always remember the night, the night he saw deaths. The night that killed his feelings.

What is the effect of repeating the words never never never