Language:
كتاب صلاة السفر
4  
Prayer (Kitab Al-Salat): Detailed Rules of Law about the Prayer during Journey
(434)
Chapter: Whoever Said He Prays One Rak'ah
(14)
باب مَنْ قَالَ إِذَا صَلَّى رَكْعَةً وَثَبَتَ قَائِمًا أَتَمُّوا لأَنْفُسِهِمْ رَكْعَةً ثُمَّ سَلَّمُوا ثُمَّ انْصَرَفُوا فَكَانُوا وِجَاهَ الْعَدُوِّ وَاخْتُلِفَ فِي السَّلاَمِ
Sunan Abi Dawud 1239
Narrated Sahl b. Abi Hathmah al-Ansari:

The prayer time of danger should be offered in the following way: The imam should stand (for prayer) and a section of the people should stand along with him. The other section should stand facing the enemy. The imam should perform bowing and prostrate himself along with those who are with him. He then should stand (after prostration) and, when he stands straight, he should remain standing. They (the people) should (in the meantime) complete their remaining rak'ah (i.e. the second one). They they should utter the salutation, and turn away while the imam should remain standing. They should go before the enemy. Thereafter those who did not pray should come forward and utter the takbir (Allah is most great) behind imam. He should bow and prostrate along with them and utter the salutation. Then they should stand and completed their remaining rak'ah, and utter the salutation.

Abu Dawud said: The tradition reported by Yahya b. Sa'id from al-Qasim is similar to the one transmitted by Yazid b. Ruman except that he differed with him in salutation. The tradition reported by 'Ubaid Allah is like the one reported by Yahya b. Sa'id, saying: He (the Prophet) remained standing.

حَدَّثَنَا الْقَعْنَبِيُّ، عَنْ مَالِكٍ، عَنْ يَحْيَى بْنِ سَعِيدٍ، عَنِ الْقَاسِمِ بْنِ مُحَمَّدٍ، عَنْ صَالِحِ بْنِ خَوَّاتٍ الأَنْصَارِيِّ، أَنَّ سَهْلَ بْنَ أَبِي حَثْمَةَ الأَنْصَارِيَّ، حَدَّثَهُ أَنَّ صَلاَةَ الْخَوْفِ أَنْ يَقُومَ الإِمَامُ وَطَائِفَةٌ مِنْ أَصْحَابِهِ وَطَائِفَةٌ مُوَاجِهَةَ الْعَدُوِّ فَيَرْكَعُ الإِمَامُ رَكْعَةً وَيَسْجُدُ بِالَّذِينَ مَعَهُ ثُمَّ يَقُومُ فَإِذَا اسْتَوَى قَائِمًا ثَبَتَ قَائِمًا وَأَتَمُّوا لأَنْفُسِهِمُ الرَّكْعَةَ الْبَاقِيَةَ ثُمَّ سَلَّمُوا وَانْصَرَفُوا وَالإِمَامُ قَائِمٌ فَكَانُوا وِجَاهَ الْعَدُوِّ ثُمَّ يُقْبِلُ الآخَرُونَ الَّذِينَ لَمْ يُصَلُّوا فَيُكَبِّرُونَ وَرَاءَ الإِمَامِ فَيَرْكَعُ بِهِمْ وَيَسْجُدُ بِهِمْ ثُمَّ يُسَلِّمُ فَيَقُومُونَ فَيَرْكَعُونَ لأَنْفُسِهِمُ الرَّكْعَةَ الْبَاقِيَةَ ثُمَّ يُسَلِّمُونَ ‏.‏ قَالَ أَبُو دَاوُدَ وَأَمَّا رِوَايَةُ يَحْيَى بْنِ سَعِيدٍ عَنِ الْقَاسِمِ نَحْوُ رِوَايَةِ يَزِيدَ بْنِ رُومَانَ إِلاَّ أَنَّهُ خَالَفَهُ فِي السَّلاَمِ وَرِوَايَةُ عُبَيْدِ اللَّهِ نَحْوُ رِوَايَةِ يَحْيَى بْنِ سَعِيدٍ قَالَ وَيَثْبُتُ قَائِمًا ‏.‏
  صحيح خ دون ذكر التسليم في الموضعين وهو موقوف ؤ ما قبله مزفوع, و فيه سلام الإمام بالطائفة الثانية وهو الآصح   (الألباني) حكم   :
Reference : Sunan Abi Dawud 1239
In-book reference : Book 4, Hadith 42
English translation : Book 4, Hadith 1235