Discussion of the hadiths regarding which the Shaykh changed his ruling, either authenticating or weakening them?

The questioner : Regarding, I mean, there are hadiths mentioned in "Sahih al-Jami'" that we find in some other works to be weak in your view; so I do not know, I mean, what is your final opinion on the hadith... and is there, I mean...?

The Shaykh : Do you want to see the earlier and later? This is clear.

The questioner : How do we know this, Shaykh?

The Shaykh : From the printing of the book, the date of the book's printing, whether it is the first edition or the second edition, and the other book in which the ruling differs from what you saw; because the issue of judging hadiths as authentic or weak is, in reality, one of the most precise of the Islamic sciences; because it requires tremendous efforts and comprehensive knowledge of the books of the Sunnah, and even with dedication and a long life, a person finds himself to be the reality of the saying of his Lord: . So what happens to us is that we devote our effort to studying a certain hadith, and we rule—for example—on the hadith as authentic, and it remains so for as many years as Allah wills, and then later we come across a manuscript that we had not previously come across, or a printed book recently printed from a manuscript, and we find that for this hadith that we had authenticated, we find a defect in a narration that we had not previously come across, and the sincerity in scientific research compels us to take into account this last narration that we came across, and to attribute a defect to the previous authentication due to a break in the chain—for example—; because there was nothing in the paths we had collected that indicated the existence of this break or that omission which some scholars call hidden omission, but it was revealed to us when we came across a narration of a hadith that we had only recently encountered, so we retracted the previous authentication from the book...
And it may be the complete opposite; that is, we rule on a certain hadith as weak, even though we had come across many of its paths, and then we are surprised—also—by a manuscript or a recently printed book in which we find either a path that strengthens those weak paths, or that this path itself constitutes the proof, so we are compelled to authenticate what we had previously weakened, and this is a matter known to everyone who has practiced this science, but one who has not practiced it is surprised, and there is no surprise in that; for we find that scholars of jurisprudence and scholars of hadith differ among themselves in authenticating the same narrator; you find Imam Ahmad or Yahya ibn Ma'in or others of the imams of critique and vindication of narrators saying about the same narrator at one time: "Trustworthy," at another time: "No harm in him," at another time: "Weak"; why? This is not ignorance, but this is knowledge; because when he ruled on his trustworthiness, he had studied the hadiths he had come across and did not find in his hadiths anything that indicated poor memorization, nor did he receive from those who preceded him among the scholars of critique and vindication a weakening of him, so he was reassured by him and authenticated him, and with time the circle of his information about the hadiths of this one whom he had authenticated expands; and then he returns and says about him: "No harm in him" or "Weak"; why? Because he found new things that compel him to retract his previous statement to a later statement, so if this is the case with the imams of hadith; then so it is with the imams of jurisprudence, and especially Imam Ahmad (may Allah have mercy on him); for we may find for him numerous statements in the same issue, and that is only due to the change in independent legal reasoning; so there is no strangeness in the change of the researcher's independent legal reasoning in authenticating and weakening, given the scarcity of the books that we can obtain today; knowing that Allah (Mighty and Majestic) had favored me and established me in the Zahiriyyah Library, which contains hundreds of thousands of books of hadiths that have not been printed, and yet the truth of Allah was realized: , for today books are printed from manuscripts other than the Zahiriyyah Library, and we find in them things that we had not previously obtained, and the scholar must be sincere in his knowledge, and not be ashamed of the people's saying: How is it that he authenticates and weakens?! Because this is the obligatory duty, and we ask Allah (Mighty and Majestic) to inspire us and you with the truth in...