What is meaning of must not

Time is not always change. time can also mean continuity, and it can mean keeping acknowledged truths in mind despite differences in circumstances. there is no better example of this in things fall apart than the retellings of the proverb about the bird named eneke, the language in both retellings is almost identical despite the length of time that has passed between their repetitions. in comparing the usages of the same proverb, achebe allows his readers to note the similarities and differences between the situations, and he them understand how this story can be applied to their own lives.