Is Sunan an-Nasa'i sahih?

Sunan an-Nasa'i is considered to be one of the six most important collections of hadiths (Kutub al-Sittah) 123. Many scholars, including al-Hafiz ibn Hajar, consider it the most authentic book after Sahih Bukhari and Sahih Muslim 3.

However, it is known that Imam an-Nasa'i included weak hadiths in his collection, which he clearly marked 13.