Are all the hadiths contained in An-Nasa'i's Sunan As-Sughra authentic, and what is the authenticity of the hadith narrated by Muslim ibn Abi Bakr: "O Allah, I seek refuge in You from disbelief, poverty, and the punishment of the grave," [to be recited] after every prayer, as it appears in An-Nasa'i's Sunan As-Sughra, Book of Seeking Refuge after Prayer?

The Sunan al-Nasa'i al-Sughra, also known as "Al-Mujtaba," is classified as the most authentic among the four Sunan books, owing to its inclusion of the highest number of authentic hadiths and the fewest weak ones. This is attributed to Imam al-Nasa'i's meticulousness in selecting authentic hadiths, based on a request from the Amir of Ramla, and his profound expertise in the science of 'ilal (hidden defects in hadiths). Despite the book's reputation for authenticity, it contains a small number of weak hadiths, which are categorized into three types: those explicitly weakened by al-Nasa'i himself within the Sunan, those he weakens in other books while remaining silent about them in the Sunan, and those he remains silent about but which are weakened by other hadith scholars. As for the hadith mentioned in the question (O Allah, I seek refuge in You from disbelief, poverty, and the torment of the grave), it is authentic, narrated by al-Nasa'i and authenticated by Al-Albani.