Ash-Shaykh Muhammad bin Saalih al-Uthaymeen, rahimahullah, was asked the following question,
عن مصل دخل و الإمام في التشهد الأخير فهل يدخل مع الجماعة أو ينتظر جماعة أخرى؟أفتونا جزاكم الله خيراً.
A person comes in for the prayer while the Imam is in the last tashahud. So, should he enter with the Jama’ah or should he wait for another Jama’ah?
فأجاب فضيلته بقوله:إذا دخل الإنسان والإمام في التشهد الأخير فإن كان يرجو وجود جماعة لم يدخل معه,
When the person enters while the Imam is in the last tashahud, if he has hopes for the occurrence of (another) jama’ah, he shouldn’t join it (i.e. the prayer)
وإن كان لا يرجو ذلك دخل معه؛لأن القول الراجح أن صلاة الجماعة لا تدرك إلا بركعة لعموم قول النبي صلي الله عليه وسلم (من أدرك ركعة من الصلاة فقد أدرك الصلاة)) .
And if he doesn’t hope that, then he should join it because the strongest opinion is that the salaatu Jama’ah is not caught except by catching a rakah from it. (This is) due to the generality of the statement of The Prophet sallahu alayhi wa salam,: (whosoever catches a rak’ah from the prayer has caught the prayer)
وكما أن الجمعة لا تدرك إلا بركعة فكذلك الجماعة,فإذا أدرك الإمام في التشهد الأخير لم يكن مدركاً للجماعة,فينتظر حتى يصليها مع الجماعة التي يرجوها,أما إذا كان لا يرجو جماعة فإن دخوله مع الإمام ليدرك ما تبقى من التشهد خير من الانصراف عنه.اهـ
Similarly (to the fact) that jumah is not caught except by catching a rak’ah from it, likewise the same for the Jama’ah prayer. So if he catches the Imam while he is in the last tashahud, then he hasn’t caught the Jamaah. Therefore, he should wait until he prays it with the jama’ah he is expecting, As for if he is not expecting another Jama’ah, then him entering with the Imam to catch what is left from the tashahud is better than him departing away
AbdulFattah bin Uthman
Shaikh Abdul-Muhsin al-‘Abbad hafidhuhallah was asked:
(Regarding) the one who reaches the Imam in the last Tashahud and he sees people enter the masjid, does he enter with the Imam or pray with another congregation?
What is apparent is if the person arrives and the people are in the original prayer praying, then he enters with them because he is one who caught the prayer and the congregation in general. And the second congregation is a difference of opinion and the congregation [going on] is the original congregation which the adhan was made for. So him entering is more deserving.
There is a difference of opinion on the second congregation: some say wait [for it], even though what is correct is a person can pray a second congregation as the Prophet sallahu alayhi wa salam said:
أَلاَ رَجُلٌ يَتَصَدَّقُ عَلَى هَذَا فَيُصَلِّيَ مَعَهُ
Is there any man who may do good with this (man) and pray along with him.
[Saheeh Sunan Abi Dawood no. 574]
Some people of knowledge say there is no second congregation. However, what is correct is they pray unless he delays from coming from the first congregation [deliberately] knowing people will pray after him. That is not allowed.
[Sharh Ibn Majah no. 64]
Faisal Ibn Abdul Qaadir Ibn Hassan