Is the supplication reported from Ali ibn Abi Talib, may Allah be pleased with him, after concluding the prayer, which states: "O Allah, forgive me for what I have put forward and what I have delayed, and what I have concealed and what I have declared, and what I have exceeded in, and what You know better than I. You are the Expediter, and You are the Delayer. There is no god but You," considered authentic, and why did Sheikh Ibn Baz not consider it among the post-prayer remembrances?

The aforementioned hadith (definition) is authentic. It was narrated by Abu Dawud and Al-Tirmidhi from Ali (may Allah be pleased with him). Its wording is: "O Allah, forgive me for what I have sent forth and what I have held back, what I have concealed and what I have declared, what I have done in excess, and what You know better than I. You are the Expediter and You are the Delayer. There is no god worthy of worship except You." It is permissible for the worshipper to make this supplication before or after the tasleem.