Mu'jam Kabir Tabarani 14171 — Some of our companions told me

Muhammad bin Sallam (may Allah have mercy on him) said: Some of our companions told me that Sayyiduna Salman bin Rabi'ah (may Allah be pleased with him) was training and testing the horses. Meanwhile Sayyiduna Amr bin Ma'di Karib (may Allah be pleased with him) passed by there on his horse, and Salman said to him: "This is a horse of mixed breed." Amr said: "No, it is a purebred." The narrator said: So Salman gave the order and the horse was kept thirsty; then he called for a basin of water and summoned the purebred horses, and they drank (standing upright). Then Amr's horse came, folded its two forelegs and drank (bending down), and that is the manner of a mixed-breed animal. Salman said to Amr: "Do you not see?" Amr said: "Yes, a half-breed recognises a half-breed." This reached Sayyiduna Umar (may Allah be pleased with him), and he wrote to him: "I have learned what you said to your commander, and I have also learned that you have a sword which you call al-Samsamah. But I have a sharp sword; by Allah, if I place it on your head, I will not lift it until I reach with it a certain thing in (your) belly (the narrator named that thing in the belly). So if you would like to know whether what I say is true, then try saying such a thing again."