The fear prayer

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that he said: "I performed the prayer of fear (salat al-khawf) with the Messenger of Allah (peace and blessings be upon him), and he (peace and blessings be upon him) led us in two rak'ahs each, except the Maghrib prayer, which was three rak'ahs."
Imam Ahmad bin Mani', Musaddad and Abu Bakr bin Abi Shaybah recorded it; there is criticism of its chain because of Hajjaj bin Artah and al-Harith bin Abdullah al-A'war.

It is narrated from Abu al-Aliyah al-Riyahi (may Allah have mercy on him) that Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him) was staying in a house (or district) of Isfahan, and in those days there was no particular fear or danger from the enemy there; but he wished to teach the people their religion and the Sunnah of their Prophet (peace and blessings be upon him). So he formed the people into two groups: one group, armed, stood in rows facing the enemy, and the other group stood behind him for the prayer. He (may Allah be pleased with him) led the group next to him in one rak'ah; then they stepped back on their heels until they reached the place of the other group, passing through one another to change places, until they (the others) came and stood behind the imam. Then he (may Allah be pleased with him) led them in another rak'ah and gave the salam. After that all the people of the first group and the second group stood and performed their remaining one rak'ah each individually, and then gave the salam. In this way the imam's two rak'ahs were completed in congregation, and the followers also completed one rak'ah each behind the imam.
Its narrators are thiqat (trustworthy), but there is a break (inqita') in its chain between Abu al-Aliyah and Sayyiduna Abu Musa al-Ash'ari (may Allah be pleased with him).

It is narrated from Sayyiduna Hudhayfah (may Allah be pleased with him) that he said: "The prayer of fear (salat al-khawf) is two rak'ahs and four prostrations; and if some sudden matter or a surprise attack of the enemy compels the one praying to hurry, then in such an emergency it becomes permissible to fight the enemy and to speak as needed during the prayer."
Imam Abu Dawud recorded it; the narrator Sharik bin Abdullah al-Qadi in its chain is open to question among the hadith scholars because of his memory. However, among the jurists there is scholarly discussion of such latitude in the rulings of salat al-mutaradah (praying while running or fighting) in a state of extreme fear.