Musannaf Ibn Abi Shayba 33:931

Affan narrated to us, he said: Ja'far ibn Sulayman narrated to us, he said: I heard al-Mu'alla ibn Ziyad say: Safwan ibn Muhriz al-Mazini had a tunnel in which he would weep, and he used to say: "I can see the place of martyrdom, and my soul is encouraging me [to seek it]."