It is narrated from ‘Iyad bin Khalifah (may Allah have mercy on him) that he heard Sayyiduna ‘Ali (may Allah be pleased with him) saying at the place of Siffin: Intelligence is in the heart, mercy is in the liver, gentleness is in the spleen, and breath is in the lungs.
Hadith Referenceالادب المفرد / كتاب / 547
Hadith Gradingالألبانی:حسن
Hadith Takhrij«حسن : أخرجه البيهقي فى شعب الإيمان : 4662 و الدار قطني فى المؤتلف و المختلف : 167/1»