I asked Anas b. Malik about shortening of prayer. He said: When the Messenger of' Allah ﷺ had covered a distance of three miles or three farsakh (Shu'ba, one of the narrators, had some doubt about it) he observed two rak'ahs.  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلاَثَةِ أَمْيَالٍ أَوْ ثَلاَثَةِ فَرَاسِخَ شُعْبَةُ الشَّاكُّ صَلَّى رَكْعَتَيْنِ  

I asked Anas b. Malik about the shortening of the prayer (while travelling). He said: When the Messenger of Allah ﷺ went out on a journey of three miles or three farsakh (the narrator Shu'bah doubted), he used to pray two rak'ahs.  

أَنَسٌ كَانَ رَسُولُ اللَّهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلاَثَةِ أَمْيَالٍ أَوْ ثَلاَثَةِ فَرَاسِخَ شُعْبَةُ شَكَّ يُصَلِّي رَكْعَتَيْنِ  

I asked Anas b. Malik about the shortening of the prayer (while travelling). He said: When the Messenger of Allah ﷺ went out on a journey of three miles or three farsakh (the narrator Shu'bah doubted), he used to pray two rak'ahs. (Using translation from Abū Dāʾūd 1201)  

«كَانَ رَسُولُ اللَّهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلَاثَةِ أَمْيَالٍ أَوْ ثَلَاثَةِ فَرَاسِخَ شُعْبَةُ الشَّاكُّ صَلَّى رَكْعَتَيْنِ»  

[Machine] About the prayer palace, I used to go out to Al-Kufa and pray two Rak'ahs before returning. Anas said: When the Messenger of Allah ﷺ would go out a distance of three miles or three farsakhs, he would doubt the boundaries of the prayer palace. This is the wording of the Hadith of Ibn Salamah, and in the narration of Abu Dawood, he would pray two Rak'ahs without mentioning his statement, "I used to go out to Al-Kufa and pray two Rak'ahs."  

عَنْ قَصْرِ الصَّلَاةِ وَكُنْتُ أَخْرَجُ إِلَى الْكُوفَةِ فَأُصَلِّي رَكْعَتَيْنِ حَتَّى أَرْجِعَ فَقَالَ أَنَسٌ كَانَ رَسُولُ اللهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلَاثَةِ أَمْيَالٍ أَوْ ثَلَاثَةِ فَرَاسِخَ شَكَّ شُعْبَةُ قَصْرَ الصَّلَاةَ لَفْظُ حَدِيثِ ابْنِ سَلَمَةَ وَفِي رِوَايَةِ أَبِي دَاوُدَ يُصَلِّي رَكْعَتَيْنِ وَلَمْ يَذْكُرْ قَوْلَهُ وَكُنْتُ أَخْرَجُ إِلَى الْكُوفَةِ فَأُصَلِّي رَكْعَتَيْنِ