What is the explanation of the Hadith: "Whoever increases the number of a people is one of them"?

The meaning of the Hadith is that whoever gathers with a group of people for an act of obedience, he is one of them, and goodness may encompass him. And whoever gathers with people of evil and disobedience, of his own free will, he is like them. The Hadith indicates that whoever increases the number of a people in disobedience, of his own free will, the punishment will be incumbent upon him along with them, and that every person's deed is judged by his intention. It also warns against accompanying oppressors and sitting with them, except for those who are compelled to do so.