صحيح البخاري Sahih Bukhari كتاب تقصير الصلاة The Book of Abridged Or Shortened Prayers (At-Taqsir)
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(5) Chapter. When a traveller leaves his original place, he can shorten his Salat (prayers).

2 hadith
Hadith 1089
حَدَّثَنَا أَبُو نُعَيْمٍ ، قَالَ : حَدَّثَنَا سُفْيَانُ ، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ ، وَإِبْرَاهِيمَ بْنِ مَيْسَرَةَ ، عَنْ أَنَسٍ رَضِيَ اللَّهُ عَنْهُ ، قَالَ : " صَلَّيْتُ الظُّهْرَ مَعَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بِالْمَدِينَةِ أَرْبَعًا وَبِذِي الْحُلَيْفَةِ رَكْعَتَيْنِ " .
Narrated Anas bin Malik: offered four rak`at of Zuhr prayer with the Prophet (p.b.u.h) at Medina and two rak`at at Dhul-Hulaifa. (i.e. shortened the `Asr prayer).
Hadith Reference Sahih Bukhari / The Book of Abridged Or Shortened Prayers (At-Taqsir) / Hadith: 1089
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة
Hadith 1090
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ ، قَالَ : حَدَّثَنَا سُفْيَانُ ، عَنْ الزُّهْرِيِّ ، عَنْ عُرْوَةَ ، عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا ، قَالَتِ : " الصَّلَاةُ أَوَّلُ مَا فُرِضَتْ رَكْعَتَيْنِ ، فَأُقِرَّتْ صَلَاةُ السَّفَرِ وَأُتِمَّتْ صَلَاةُ الْحَضَرِ " ، قَالَ الزُّهْرِيُّ : فَقُلْتُ لِعُرْوَةَ : مَا بَالُ عَائِشَةَ تُتِمُّ ، قَالَ : تَأَوَّلَتْ مَا تَأَوَّلَ عُثْمَانُ .
Narrated `Aisha: "When the prayers were first enjoined they were of two rak`at each. Later the prayer in a journey was kept as it was but the prayers for non-travelers were completed." Az-Zuhri said, "I asked `Urwa what made Aisha pray the full prayers (in journey)." He replied, "She did the same as `Uthman did."
Hadith Reference Sahih Bukhari / The Book of Abridged Or Shortened Prayers (At-Taqsir) / Hadith: 1090
Hadith Grading محدثین: أحاديث صحيح البخاريّ كلّها صحيحة