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
[Machine] I used to go out to Al-Kufa to pray two units of prayer before returning. Anas said, "Whenever the Messenger of Allah ﷺ went on a journey of three miles or three farsakhs, he would pray two units of prayer."
كُنْتُ أَخْرُجُ إِلَى الْكُوفَةِ فَأُصَلِّي رَكْعَتَيْنِ حَتَّى أَرْجِعَ وَقَالَ أَنَسٌ كَانَ رَسُولُ اللهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلَاثَةِ أَمْيَالٍ أَوْ ثَلَاثَةِ 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. (Using translation from Abū Dāʾūd 1201)
«كَانَ رَسُولُ اللَّهِ ﷺ إِذَا خَرَجَ مَسِيرَةَ ثَلَاثَةِ أَمْيَالٍ أَوْ ثَلَاثَةِ فَرَاسِخَ شُعْبَةُ الشَّاكُّ صَلَّى رَكْعَتَيْنِ»