(a) It is narrated from Nafi' that when Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) was asked about the fear prayer, he replied that the imam and one group should go forward and pray while the other remains facing the enemy; then he narrated the complete hadith.
(b) In the hadith, Ibn Umar (may Allah be pleased with them both) said: "If the fear is greater than that, they should pray both on foot and riding, whether facing the qiblah or not."
(c) It is established through Musa bin Uqbah from Nafi', from Sayyiduna Ibn Umar (may Allah be pleased with them both), from the Prophet (peace and blessings be upon him). Its proper place is the Book of the Fear Prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2228