Regarding "Sunan al-Tirmidhi" and his unique use of the phrase: "This is a hasan hadith."

The questioner : A question regarding "Sunan al-Tirmidhi" asks: Does al-Tirmidhi's unique use of the phrase "This is a hasan hadith" mean that the hadith is weak?

The Shaykh : This is not a rule, and the ruling varies depending on the people. The general public must rely on the authentication and weakening of their scholars, because they do not have the knowledge to distinguish between the error or mistake of those who authenticated or weakened among the early scholars. As for one who has a share in this knowledge and knows how a hadith is authenticated and how it is weakened, he may critique those who authenticated or weakened, whether it is al-Tirmidhi or someone else. In addition to the previous answer to this question, I want to draw attention to the fact that al-Tirmidhi has specific terminologies in his book "al-Sunan." Students of knowledge must pay attention to this. The first terminology is saying: "This is a hasan gharib hadith." The other terminology is saying: "This is a hasan hadith." In this terminology, it means the opposite of what comes to the mind of a beginner in this science. It means that the chain of this hadith is weak. The hadith in which he says "hasan hadith" means that its chain here is weak. For example, you will often find him narrating a hadith through the route of 'Abd Allah ibn Lahi'ah. 'Abd Allah ibn Lahi'ah was a Muslim judge, and those engaged in the biographies of narrators know that he is weak due to his poor memory. Nevertheless, you will see him say in some of the hadiths he narrates through his route: "Hasan hadith," and remain silent. There are many like Ibn Lahi'ah. So what does his saying "hasan hadith" mean? It means: good in the aggregate of its routes, not through this route. This route is weak. If you do not know the chain of this route, you must judge that there is weakness in this chain, as long as he said only "hasan hadith."
As for when he says: "Hasan gharib hadith," he means that it is a hasan hadith in itself, and he only considered it strange because one of its narrators is unique in narrating it. Therefore, when al-Tirmidhi says "hasan hadith" and one of us finds a man known for weakness in its chain, one should not rush to criticize al-Tirmidhi and say, "It is known that al-Tirmidhi is lenient!" Because by this statement, he means that it has other routes. If you want to research and verify, follow up in your research and look to see if it has other routes or not. If you find them, and you often do, then you are assured that his saying "hasan hadith" means "hasan li-ghayrihi" (good due to other evidence), unlike his saying "hasan gharib hadith," which means that it is good in itself. Regardless of whether he was correct or wrong in that, or whether he was lenient or not, that is a second matter. It is known from his biographies of narrators that, for example, he authenticates the hadith of Kathir ibn 'Abd Allah ibn 'Awf, Kathir ibn 'Abd Allah ibn 'Awf al-Muzani, even though this man is accused of lying. Al-Tirmidhi mentions this in the biography of Kathir, and al-Tirmidhi authenticates hadiths for him. Therefore, scholars do not rely on his authentication. Look at how he says "scholars do not rely on it"; that is, those who are capable of knowing al-Tirmidhi's leniency when he authenticates some hadiths, such as the hadiths of this Kathir. As for non-scholars, they have no choice but to follow the people of knowledge.