Mishkat al-Masabih 23 Medicine and Spells كتاب الطب والرقى 51

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»

Abu Huraira reported God’s messenger as saying: “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.”