Short answer
The janazah prayer is fard kifayah, a communal duty. If some Muslims pray it, the duty is lifted from everyone; if no one prays it, everyone who knew of the death and could have prayed is sinful. The four schools agree.
Salat al-janazah is fard kifayah. Its fard parts are the four takbirs and standing; the praise (thana), the salawat on the Prophet ﷺ and the dua for the dead are sunnah. It needs wudu, a clean place and facing the qiblah like any prayer, but it has no ruku, sujud, adhan or iqamah.
The four schools agree on this.
Explanation
Every Muslim who dies has a right to be washed, shrouded, prayed over and buried. These are all fard kifayah (a communal duty): Allah asks the community as a whole to make sure they happen. Once enough people do it, the rest are free of the duty. If the whole community leaves it, everyone who knew and was able shares the sin. The four schools agree on this.
The Prophet ﷺ prayed over his Companions, ordered prayer over those he himself held back from, and counted following funerals among the rights one Muslim has over another. When a man was brought who had died owing a debt he could not pay, the Prophet ﷺ told the others, "Pray over your companion." So even when he had a reason to step back, he did not let the prayer be skipped.
What makes the prayer valid in the Hanafi school:
- The dead person is a Muslim, has been washed (or given tayammum when washing is impossible) and is placed in front of the imam.
- The people praying have wudu, cover their awrah and face the qiblah.
- Four takbirs said while standing. Without the four takbirs, the prayer has not been done.
Although the duty falls on the community, each person who joins earns a great reward, and the more who pray, the better for the dead. See the reward for attending a janazah. For the step-by-step method, see how to pray janazah.
The evidence
Quran, Surah At-Tawba 9:84
وَلَا تُصَلِّ عَلَىٰٓ أَحَدٍۢ مِّنْهُم مَّاتَ أَبَدًۭا وَلَا تَقُمْ عَلَىٰ قَبْرِهِۦٓ ۖ إِنَّهُمْ كَفَرُوا۟ بِٱللَّهِ وَرَسُولِهِۦ وَمَاتُوا۟ وَهُمْ فَٰسِقُونَ ﴿٨٤﴾
And do not pray [the funeral prayer, O Muhammad], over any of them who has died - ever - or stand at his grave. Indeed, they disbelieved in Allah and His Messenger and died while they were defiantly disobedient.
Forbidding the funeral prayer over hypocrites shows that praying over believers is the established practice.
Sahih al-Bukhari 2295
Sahih... صلوا على صاحبكم ...
"Pray over your companion."
The Prophet ﷺ made sure the prayer still happened even when he held back himself.
Sahih al-Bukhari 1240
Sahih... حق المسلم على المسلم خمس رد السلام وعيادة المريض واتباع الجنائز ...
"The rights of a Muslim over a Muslim are five: returning the greeting, visiting the sick, following funerals..."
Following the funeral is a right owed to every Muslim.
Sahih Muslim 947
Sahih... يبلغون مائة كلهم يشفعون له إلا شفعوا فيه ...
"No dead person is prayed over by a group of Muslims reaching a hundred, all interceding for him, except that their intercession for him is accepted."
The prayer is an intercession, so more people praying is better.
Where the ruling is recorded
- al-Hidaya, Kitab al-Salah, Bab al-Jana'iz, section on the funeral prayer. The funeral prayer is a communal obligation; the takbirs and standing are its pillars.
- Radd al-Muhtar (Ibn Abidin), Kitab al-Salah, Bab Salat al-Janazah. Its conditions, pillars and sunnahs.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.