عَنْ أَبِي هُرَيْرَةَ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الْمَعِدَةُ حَوْضُ الْبَدَنِ وَالْعُرُوقُ إِلَيْهَا وَارِدَةٌ فَإِذَا صَحَّتِ الْمَعِدَةُ صَدَرَتِ الْعُرُوقُ بِالصِّحَّةِ وَإِذَا فَسَدَتِ الْمَعِدَةُ صَدَرَتِ الْعُرُوقُ بِالسقمِ»

“The stomach is the tank of the body and the veins go down to it. When the stomach is healthy the veins come back in a healthy condition, but when it is in a bad condition they return diseased.”