The fourth category is following the imam.

Following the imam is the sunnah. It means that a person begins the actions of the prayer as soon as his imam begins them, but without moving simultaneously with him.

For example, when the imam bows, you should bow, even if you have not completed the recommended recitation—even if only one verse remains—because completing it would cause you to lag behind, so do not complete it. Similarly, in prostration, when the imam rises from prostration, follow the imam. Following him is better than remaining in prostration to supplicate Allah, because your prayer is connected to the imam, and you are now commanded to follow your imam.

Issue: If the prayer is called to commence, the imam says the opening takbir and recites al-Fatihah, but a man does not join the imam, saying, “When the imam bows, I will stand and bow,” and so he remains where he is; or two men remain talking, and when the imam bows, they stand and bow with him—should we say that this renders his prayer invalid because he did not recite al-Fatihah? Or should we say that he is a latecomer who caught the bowing, and thus his prayer is valid, since before entering the prayer he is not required to recite al-Fatihah?

The answer: I am inclined to the view that, so long as he has not entered the prayer, the rulings of the prayer do not apply to him. However, we say: You have erred and deprived yourself of much good, for the following reasons:

First: You missed the virtue of saying the opening takbir after the imam, and of reciting al-Fatihah and the additional surah, if one is recited.

Second: You exposed yourself to missing a rak'ah, because some scholars hold that his rak'ah is invalid.