´It was narrated from Safiyyah bint Shaimah that a woman said:` I saw the Messenger of Allah hastening at the bottom of the valley and he said: "The river bed should not be crossed except with vigor."
Explanation & Benefits
Hafiz Muhammad Ameen
Commentary:
By "the bottom of the valley" is meant the low-lying area between the green lights situated between Safa and Marwah, that is, the place between the inclines of the two hills. In the event of rain and the like, water would flow through this area, which is why it was called a valley (wadi) or a watercourse (masil). Nowadays, it is referred to as "Milayn Akhdarayn" (the two green markers).
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 2983