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." (Sahih) Chpater 178. The Place Where One Should Walk  

رَأَيْتُ رَسُولَ اللَّهِ ﷺ يَسْعَى فِي بَطْنِ الْمَسِيلِ وَيَقُولُ لاَ يُقْطَعُ الْوَادِي إِلاَّ شَدًّا