مسائل المنتخبه (Articles Of Islamic Acts) - الخوئي، السيد أبوالقاسم - الصفحة ٣٠٧ - Congregational Prayers

it is so high that it cannot be said that they have gathered together, the congregation is not in older.
١٤٢٦. If there is a distance of one person. whose prayers is void, between the persons who are standing in the row, they can follow the Imam. However, if there isa distance of a few persons, whose prayers are void, between them or the distance becomes much owing to some other reason, they cannot follow the Imam.
١٤٢٧. If after the takbir of the Imam the persons in the front row are ready for prayers and are about to say takbir, a person standing in the back row can also saytakbir. However, the recommended precaution is that he should wait so that the takbir of the front row may be completed.
١٤٢٨. If a person knows that the prayers of one of the followers of front rows is void, he cannot follow the Imam in the back rows. but he can follow the Imam. ifhe does not know whether or not the prayers of those persons is in order.
١٤٢٩. If a person knows that the prayer of the Imam is void - for example, if he knows that the Imam is without ablutions. though the Imam may not be attentive tothis fact himself - he cannot follow that Imam.
١٤٣٠. If the follower learns after the prayers that the Imam was not a just person ( or was an unbeliever, or for some reason, for example, owing to his not havingperformed ablutions, his prayers was void, but he himself (i.e. the follower) has not performed any act which makes individual prayers void, even it performed by mistake(e.g. an additional bowing) his prayers is valid.
١٤٣١. It a person doubts while offering prayers whether he has followed the Imam or not, and if he was offering prayers under the impression that he was offeringcongregational prayers and it is probable that owing to forgetfulness he did not make the intention of congregational prayers and if (at the time doubt