Explanation of the words of Imam al-Nawawi (may Allah have mercy on him) regarding what he quoted: "

The Shaykh : In the name of Allah, the Most Gracious, the Most Merciful:
The author (may Allah have mercy on him) said, in what he quoted from al-Hasan ibn 'Ali ibn Abi Talib (may Allah be pleased with them both) in the chapter on truthfulness: “Leave” means abandon, and “that which causes you doubt” (with the yā' open) means that you are uncertain about it and do not feel at ease with it, meaning that which is free from doubt.
This hadith is one of the hadiths of the Nawawi Forty; it is a comprehensive and important hadith, and it is a great chapter among the chapters of scrupulousness and caution. The scholars of knowledge (may Allah have mercy on them) followed this path in the chapters of jurisprudence: taking the side of caution. They mentioned many things for this, for example: a person whose garment is contaminated with impurity, and he does not know whether it is in the front of the garment or the back. If he washes the front, he has doubt because it might be in the back; and if he washes the back, he has doubt because it might be in the front. So what is the caution? The caution is to wash both the front and the back until his doubt is removed and he is at ease. Likewise, if a person is uncertain in his prayer whether he prayed two rak'ahs or three, and nothing is more probable for him, then if he takes the two, he has doubt that he might have fallen short; and if he takes the three, he has doubt that he might not have fallen short, but he remains anxious. So what does he do? He acts according to that in which there is no doubt, so he acts according to the lesser number. If he is uncertain whether it is three or four, let him make it three; if it is three or two, let him make it two, and so on.
The important point is that this hadith is a principle among the principles of jurisprudence: that which you are uncertain about, leave it for that in which there is no doubt. Also, it contains psychological training, which is that a person should be in a state of reassurance, not anxiety. Because many people, when they take what they are uncertain about, become anxious if they are alive in heart; they are always thinking, with their hearts pounding, “Perhaps I did it, perhaps I left it.” So when the doubt is cut off by certainty, that is removed from him. The Prophet (peace and blessings be upon him) said: : And this is the point of relevance of this hadith for this chapter, the chapter of truthfulness, : its owner never regrets it. If a person informs with truth, he does not regret, and he does not say: “I wish, I wish,” because truth is salvation, and the truthful ones, Allah the Exalted saves them by their truthfulness. You will find the truthful person always at ease, because he does not regret something that happened or something that will happen in the future, because he has told the truth, and whoever tells the truth is saved. As for lying, the Prophet (peace and blessings be upon him) stated that it is doubt. For this reason, you will find the first one to doubt the liar is his own self; the liar’s own self doubts whether people will believe him or not. For this reason, you will find the liar, when he informs you of news, stands and swears, swearing by Allah that it is true, so that you do not doubt his news, even though it is a place of doubt. You will find, for example, the hypocrites swear by Allah that they did not say it, but they are in doubt. Allah the Exalted said: So lying is undoubtedly doubt, anxiety for the person; the person doubts whether people knew of his lie or not, so he remains in doubt and disturbance. So we take from this hadith: that it is obligatory for a person to leave lying for truthfulness, because lying is doubt, and truthfulness is reassurance. And the Prophet (peace and blessings be upon him) said: , and success is from Allah.