If a company of Muslims numbering one hundred pray over a dead person, all of them interceding for him, their intercession for him will be accepted.  

عَنِ النَّبِيِّ ﷺ قَالَ مَا مِنْ مَيِّتٍ يُصَلِّي عَلَيْهِ أُمَّةٌ مِنَ الْمُسْلِمِينَ يَبْلُغُونَ مِائَةً كُلُّهُمْ يَشْفَعُونَ لَهُ إِلاَّ شُفِّعُوا فِيهِ قَالَ فَحَدَّثْتُ بِهِ شُعَيْبَ بْنَ الْحَبْحَابِ فَقَالَ حَدَّثَنِي بِهِ أَنَسُ بْنُ مَالِكٍ عَنِ النَّبِيِّ ﷺ  

I heard the Prophet ﷺ say: If any Muslim dies and forty men associate nothing with Allah stand over his bier. Allah will accept them as intercessors for him.  

سَمِعْتُ النَّبِيَّ ﷺ يَقُولُ مَا مِنْ مُسْلِمٍ يَمُوتُ فَيَقُومُ عَلَى جَنَازَتِهِ أَرْبَعُونَ رَجُلاً لاَ يُشْرِكُونَ بِاللَّهِ شَيْئًا إِلاَّ شُفِّعُوا فِيهِ  

"When Malik bin Hubairah performed Salat for a funeral and the people were few he would divide them into three groups (rows) then say: 'The Messenger of Allah said: "For whomever three rows perform Salat, then it is granted."  

فَتَقَالَّ النَّاسَ عَلَيْهَا جَزَّأَهُمْ ثَلاَثَةَ أَجْزَاءٍ ثُمَّ قَالَ قَالَ رَسُولُ اللَّهِ ﷺ مَنْ صَلَّى عَلَيْهِ ثَلاَثَةُ صُفُوفٍ فَقَدْ أَوْجَبَ قَالَ وَفِي الْبَابِ عَنْ عَائِشَةَ وَأُمِّ حَبِيبَةَ وَأَبِي هُرَيْرَةَ وَمَيْمُونَةَ زَوْجِ النَّبِيِّ ﷺ