Elmore Leonard’s Rule #3 on Writing
Never use a verb other than ”said” to carry dialogue.
The line of dialogue belongs to the character; the verb is the writer sticking his nose in. But said is far less intrusive than grumbled, gasped, cautioned, lied. I once noticed Mary McCarthy ending a line of dialogue with ”she asseverated,” and had to stop reading to get the dictionary.
Source: New York Times