When a traveller leaves his original place, he can shorten his Salat (prayer)

Narrated Anas bin Malik:

offered four rak`at of Zuhr prayer with the Prophet (ﷺ) at Medina and two rak`at at Dhul-Hulaifa. (i.e. shortened the `Asr prayer).

حَدَّثَنَا أَبُو نُعَيْمٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ مُحَمَّدِ بْنِ الْمُنْكَدِرِ، وَإِبْرَاهِيمَ بْنِ مَيْسَرَةَ، عَنْ أَنَسٍ ـ رضى الله عنه ـ قَالَ صَلَّيْتُ الظُّهْرَ مَعَ النَّبِيِّ صلى الله عليه وسلم بِالْمَدِينَةِ أَرْبَعًا، وَبِذِي الْحُلَيْفَةِ رَكْعَتَيْنِ‏.‏

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."

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ ـ رضى الله عنها ـ قَالَتِ الصَّلاَةُ أَوَّلُ مَا فُرِضَتْ رَكْعَتَيْنِ فَأُقِرَّتْ صَلاَةُ السَّفَرِ، وَأُتِمَّتْ صَلاَةُ الْحَضَرِ‏.‏ قَالَ الزُّهْرِيُّ فَقُلْتُ لِعُرْوَةَ مَا بَالُ عَائِشَةَ تُتِمُّ قَالَ تَأَوَّلَتْ مَا تَأَوَّلَ عُثْمَانُ‏.‏