Should the funeral prayer be offered for the shaheed when he is killed?

The shaheed (martyr) is a Muslim who dies
fighting the kuffaar and for that reason. See al-Mawsoo’ah al-Fiqhiyyah, Kuwait edition, 26/272 

The majority of scholars said that the
funeral prayer should not be offered for him. That is the view of Imam Maalik and al-Shaafa’i, and the more correct of the two views narrated from
Imam Ahmad. See al-Mughni, 2/334. That is because the Prophet (peace and blessings of Allaah be upon him) did not pray for the martyrs
of Uhud (narrated by al-Bukhaari, 1347), and because the purpose behind the funeral prayer is to intercede for the deceased. But the martyr
receives expiation for everything (so he has no need of intercession), apart from debt; debt is not waived because of martyrdom, rather it remains
owed by the deceased. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah
have mercy on him) said: 

It is not prescribed to offer the funeral
prayer for the martyrs who die in battle, or to wash them, because the Prophet (peace and blessings of Allaah be upon him) did not offer the
funeral prayer for the martyrs of Uhud, neither did he wash them. This was narrated by al-Bukhaari in his Saheeh (1347) from Jaabir ibn
‘Abd-Allaah (may Allaah be pleased with him). 

Majmoo’ Fataawa Ibn Baaz,
13/162 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy
on him) said: 

No one among the people – neither the imam nor anyone else – should offer the funeral prayer
for the shaheed, because the Prophet (peace and blessings of Allaah be upon him) did not offer the funeral prayer for the martyrs of Uhud,
and because the purpose behind the funeral prayer is to intercede for the deceased. The Prophet (peace and blessings of Allaah be upon him)
said: “There is no Muslim man who dies, and forty men who do not associate anything in worship with Allaah offer the funeral prayer for him, but
their intercession with Allaah for him will be accepted.” But the martyr receives expiation for everything apart from debt, because debt cannot be
waived by martyrdom, rather it remains owed by the deceased and is to be paid off from his estate if he left anything behind. Otherwise if he took
it with the intention of paying it back, Allaah will pay it back on his behalf. 

Al-Sharh al-Mumti’,
5/367 

Some of the scholars were of the view that it
is permissible to offer the funeral prayer for the shaheed – but it is not obligatory. This was narrated from Imam Ahmad (see al-Mughni,
2/334). That is because of the following ahaadeeth: 

1 – It was narrated from Shaddaad ibn al-Haad
that a man from among the Bedouin came to the Prophet (peace and blessings of Allaah be upon him) and believed in him and followed him, then
he said: “I will migrate with you.” They stayed there for a while, then they engaged in fighting the enemy. He was brought to the Prophet
(peace and blessings of Allaah be upon him), and he had been struck by an arrow… Then the Prophet (peace and blessings of Allaah be upon him)
shrouded him in his cloak, then he placed him in front of him and offered the funeral prayer for him. 

Narrated by al-Nasaa’i; classed as saheeh by
al-Albaani in Ahkaam al-Janaa’iz, p. 82 

2 – It was narrated from ‘Abd-Allaah ibn al-Zubayr that on the day of Uhud, the Messenger of
Allaah (peace and blessings of Allaah be upon him) ordered that Hamzah be wrapped in his cloak, then he offered the funeral prayer for him.
He said takbeer nine times, then the slain were brought and laid in rows, and he offered the funeral prayer for them and for him with them. 

Narrated by al-Tahhaawi in Ma’aani
al-Athaar, 1/290; classed as hasan by al-Albaani in Ahkaam al-Janaa’iz, p. 82. 

Among those who favoured this view was Shaykh
Naasir al-Deen al-Albaani, may Allaah have mercy on him. See Ahkaam al-Janaa’iz, p. 81.