Reference: I’laam al-Mu’aasireen bi-Fataawa Ibn ‘Uthaymeen – Page 59
Question: A person [intending to perform the congregational prayer] finds the imaam in the final tashahhud, should he join the congregation or wait for another congregation [to gather for the prayer]? Provide us with a ruling and may Allaah reward you with good.
Response: If a person [intending to perform the congregational prayer] enters and the imaam is in the final tashahhud, then if he anticipates the gathering of another congregation he should not join the imaam, and if he does not anticipate the gathering of another congregation then he should join him. This is because the preponderant opinion is that the [reward for the] congregational prayer is not attained unless one joins the prayer before the final rukoo’ – due to the generality of his ﷺ statement:
«Whoever catches the [final] rak’ah of the prayer, then he has attained the [reward for the congregational] prayer», [transmitted by al-Bukhaaree – 580 and Muslim – 607]
And just as the [reward for the] jumu’ah [prayer] is not attained unless one joins the prayer before the final rukoo’, likewise is the case for the congregation[al prayer].
So, if he finds the imaam in the final tashahhud, [and joins the congregation] then he will not have attained the [reward for the] congregation[al prayer], otherwise he can wait [the gathering of another congregation] and pray with this [new] congregation. If however he does not anticipate the gathering of another congregation, then his joining the imaam in whatever is left of the [final] tashahhud is better than abstaining from it.
