The word(s) "joining" appears 4 time(s) in 4 verse(s) in Quran in Saheeh International translation.

(1) And [recall] when We took the covenant from the Children of Israel, [enjoining upon them], "Do not worship except Allah; and to parents do good and to relatives, orphans, and the needy. And speak to people good [words] and establish prayer and give zakah." Then you turned away, except a few of you, and you were refusing.

(2) And let there be [arising] from you a nation inviting to [all that is] good, enjoining what is right and forbidding what is wrong, and those will be the successful.

(3) And whoever turns his back to them on such a day, unless swerving [as a strategy] for war or joining [another] company, has certainly returned with anger [upon him] from Allah, and his refuge is Hell - and wretched is the destination.

(4) And when a surah was revealed [enjoining them] to believe in Allah and to fight with His Messenger, those of wealth among them asked your permission [to stay back] and said, "Leave us to be with them who sit [at home]."