MLA

Nawawī, 1233-1277. Kitāb al-arbaʻīn. [n.d., but before 1835]. https://collections.library.yale.edu/catalog/10985835.

APA, 6th edition

Nawawī, 1233-1277. ([n.d., but before 1835])[Kitāb al-arbaʻīn]. https://collections.library.yale.edu/catalog/10985835.