Abu’l-Darda’ (r) said:
“Be a teacher or a student or one who listens in or one who would love to (but can’t) but don’t be a fifth so that you be destroyed,”
Hasan al-Basri (r) said that the fifth person is an innovator.
Others said it is the one who doesn’t like to seek knowledge, and others said it is those who don’t love the people of knowledge.
– From a comment by AE