Manual:$wgMaxArticleSize

Details
Also used for the post-expand include size and template argument size which are used to abort parsing the page when then the pre-processed wikitext that results from transcluding templates would be too large. If the article doesn't render as expected and the HTML source has errors like  or, when you get an error during importing about the text of the revision exceeding the maximum allowable size, then you can use this setting to adapt the maximum page size in kibibytes allowed on your wiki. In general it is a preferred approach to split the respective page into several smaller pages.

If you increase this value, you should generally also increase accordingly (a usual value would be  ).