In some other narrations of the hadith, the addition to the end is “Verily good is what settles in one’s heart and evil is that which is doubtful.” This will be discussed in some of the ahadith coming up later in the 40 Hadith. The last thing to mention is that one of the ways to know what is doubtful is to look at things as opposites. If you’re trying to figure out if something is doubtful or permissible, you can look at its opposite. When you see the opposite sometimes it’s easier and clearer to understand the nature of that thing.
