What is meant by each of "a benefited brother," "a firm word," and "an awaited mercy" in the Hadith: "The companion of the mosque has three characteristics: a benefited brother, or a firm word, or an awaited mercy"?

The aforementioned Hadith clarifies that a person who sits in the mosque will not be deprived of three benefits: a brother benefited (you get to know a sincere brother), or a well-founded word (you hear beneficial speech), or an awaited mercy (the angels pray for mercy and forgiveness for you as long as you are sitting).