Joining an imām in prayer whose intention was for a different prayer
In a situation where no sooner a person starts prayer by standing up, saying Allahu Akbar and sitting down to join a congregation, the imam ends the prayer with salaam, it is still as if he has prayed as a part of the congregation provided that the imam has not uttered Assalamu Alaikum even to the extent of “Assalam” before he joins. He can continue the salaah by standing up preferably after reciting tashahhud.
In a situation where a person says Allahu Akbar to join the imam and the Imam ends his prayer by saying salaam, he need not sit down and should continue his prayer. Again it is as if he prayed with the congregation.
However when a person joins a congregation after the first Assalamu Alaikum has been said even so much as ‘Assalam’ he will not be considered to have prayed with the congregation.
Issue of Proximity – (محاذات)
If a mature woman prays next to a man without any partition, it will nullify the prayer of man if the Imam leading the congregation intended to lead women as well. If however, the Imam didn’t intend for women congregation, men’s prayer will be valid but woman’s prayer will be invalid.
When in such a situation, one can ensure the validity of prayer by doing one of the followings:
- keeping an object an arm span long and a finger-breadth wide in between.
- moving ahead of her such that her toes remain behind his heels.
- putting something under his feet to elevate such that he is above the ankles of the woman.
If he is praying behind the woman, then an arm-breadth wide plank should be erected in between or he is above the head of the woman. Failing to do any of these will nullify his prayers.
Where should wife stand whilst praying with her at home?
When praying fard salaah at home it is better to pray in congregation even if there are only women available.
The woman should stand behind the leading man even when there is a single woman praying along with him. This is different when two men are praying together as they stand side by side with the imam’s heels slightly ahead of his follower.
 Ahsan ul Fatawa vol 3, pg 365; Fatawa Mahmoodiyyah vol 16, pg 228