350 – Anas (may Allah be pleased with him) reported: “Whenever the Messenger of Allah ﷺ had set out and covered a distance of three miles—or farsakhs—he would perform two rakʿahs.” Related by Muslim (1).

Lexical notes on the ḥadīth
– “miles or farsakhs”: a doubt on the part of the transmitter, Shuʿbah ibn al-Ḥajjāj; it is not meant to describe different scenarios.
– Miles (sing. mīl): one mile is approximately 1,600 meters.
– Farsakhs (sing. farsakh): one farsakh equals three miles. Both terms are Persian units that entered Arabic usage.
– “He prayed two rakʿahs”: i.e., he shortened every four-rakʿah prayer to two; this concerns ẓuhr, ʿaṣr, and ʿishāʾ.

Points derived from the ḥadīth
1 – Whenever the Prophet ﷺ departed from his place of residence—Madinah—and had covered about three miles or farsakhs, he would shorten the four-rakʿah prayers to two.
2 – This shows that, at that distance, the travel concessions—such as combining and shortening the prayers—become permissible; the ḥadīth, however, is not establishing the minimum distance for shortening, for that is derived from other evidence.
3 – The phrase “when he went out” means “when he set out intending to cover that distance,” not that he would wait until the distance was actually traversed before shortening.
4 – One farsakh equals three miles, and one mile is roughly 1,600 meters; the narrator’s wording, “miles or…"