The worshippers in the front row are rewarded more than the worshippers in the back row, according to a Saying of the Holy Prophet(sa). The reason is that those who come early, continue remembering God Almighty while they wait for the Prayer to commence; naturally they are in communion with Allah during more time as compared to the people who come later.
Again, the Holy Prophet(sa) instructed that a new row should not be started until the previous one is fully filled. It is therefore clear that those who come early and occupy the first row and spend more time in the remembrance of God Almighty will be rewarded more than those who come just in time while the Takbir is being recited or even later. These are the people who occupy the back rows.

If the Prayer has already started, the latecomer should join in the congregation in the position in which he finds them. For example, if they are in the Standing position, he should start his Prayer in standing position but if they are prostrating, he should join the congregation in prostration.
When the Imam ends the congregational Prayer by saying the Salutation, i.e. Assalamu ‘Alaikum wa Rahmatullah and turning his face towards the right and towards the left, the person who joined the Prayer later should go into Qiyam position and complete the remaining Rak‘at of his Prayer individually.

Salat consists of units. Each unit is called a Rak‘at. There are two Rak‘at and four Rak‘at Prayers in the Fard of obligatory Prayer.
Each unit or Rak‘at consists of the following essential component parts:

1. The posture of standing called Qiyam.

2. The posture of Bowing down with the hands on one’s knees called Ruku‘.

3. The position of Standing erect again with arms on the sides called Qaumah.

4. The position of Prostration called Sajdah. There are two Prostrations in one Rak‘at.

5. Jilsah: The position of sitting in between the two Prostrations.

6. Qa‘dah: The position of sitting after the two Prostrations. If a latecomer joins the congregation before or during the Ruku‘, then it is deemed that he had offered that Rak‘at and he does not have to offer it again at the end of the Prayer. If he misses both the initial Standing position (Qiyam) and the Bowing position (Ruku‘) and joins later in that Rak‘at he has to offer the whole Rak‘at again at the end of the Prayer when the Imam has done both salutations.

Once the congregational Prayer has begun, one should not commence with Sunnat and Nafl Prayer. If someone is already engaged in Sunnat Prayer when the Imam starts the Prayer, and he finds himself in the middle of a row formed for the congregational Prayer, he should terminate his Prayer immediately and join in the congregation. If he is offering his Sunnat or Nafl Prayer away from the Prayer Service and he thinks that he can join in the congregation without losing much of the first Rak‘at, he may complete his Prayer; otherwise he should terminate his Prayer and join in the congregation.

If the Prayer has already started, it is forbidden for a worshipper to run and join in the congregation.

Out of respect for their chastity and honour, women are not advised to stand for Prayer in front of men. For this reason, the rows of women are always behind the men’s rows. This gives the women complete freedom to offer their Prayers in the back rows without being embarrassed by the presence of men. It is preferable however, to have a separate enclosure for women. It also follows from the above that a woman cannot lead a congregation of men, but can lead a congregation of women. This means that she can lead a congregation consisting of children of either sex among the worshippers, but not adult men.

Women need not say Adhan for their congregational Prayers. The female Imam stands in the middle of the first row, according to common practice, and not ahead of the congregation as in the case of a male Imam.

If the Imam commits a mistake while leading the congregation, the following method is adopted to point it out to him:

1. If the mistake is an incorrect recitation of the Holy Quran, or the Imam has forgotten a verse of the Holy Quran, anyone in the congregation who clearly remembers the correct wording, should remind the Imam by reciting the correct verse in a clear and audible voice.

2. If the Imam commits any other mistake, a member of the congregation should draw his attention to it by saying Subhanallah. Subhanallah means ‘Allah is free from all faults.’ It gives a cue to the Imam that he may have committed a mistake. If so, the Imam should rectify his mistake. If he does not correct his error, the congregation has to follow him and no one has the right to differ with him during the Prayer. They must follow the Imam even in his mistake. However, he should be told of his mistake after the Prayer. Then he should lead the congregation to two additional Prostrations by way of condoning the mistake before turning his face to right and left and again repeating Assalamu ‘Alaikum wa Rahmatullah. These are called Sujud-us-Sahv or the Prostrations of condonement.

If a woman wants to draw the attention of the Imam to a mistake which he had committed, she is not allowed to say Subhanallah aloud; instead, she should clap her hands. The sound of clapping from women conveys to the Imam the message that he has committed a mistake. In the case where a female Imam commits a mistake during Prayer, her followers may draw her attention to it by either reciting the verse correctly or by saying Subhanallah, as the case may be.

The Imam should not prolong the congregational Prayer to the extent that the worshippers who are praying with him get tired. He should keep in mind that there might be people of old age or who are sick or weak in the congregation and also people who have to attend to other duties after the Prayer.