It is narrated from Sayyiduna Umayr bin Qatadah al-Laythi (may Allah be pleased with him) that he said: There was a question in my heart which had grieved me. I had not asked the Messenger of Allah (peace and blessings be upon him) about it, nor had I heard anyone ask him about it, so I kept looking for a suitable moment with him (peace and blessings be upon him). One day I came in while he (peace and blessings be upon him) was performing ablution, and I found him in two states in which I liked to find him: I found him free and in good spirits. I said: "O Messenger of Allah, permit me to ask you something." He (peace and blessings be upon him) said: "Yes, ask whatever you wish." I said: "O Messenger of Allah, what is faith?" He (peace and blessings be upon him) said: "Generosity and patience." I asked: "Which of the believers is best in faith?" He (peace and blessings be upon him) said: "The one with the best character." I asked: "Which of the Muslims is best in Islam?" He (peace and blessings be upon him) said: "The one from whose hand and tongue the other Muslims are safe." I asked: "Which jihad is best?" He (peace and blessings be upon him) lowered his head and remained silent for a long time, until I feared that I had burdened him, and I wished that I had not asked this question, for only the day before I had heard him say: "The greatest criminal among the Muslims is the one who asks about something that was not forbidden to them, and it is then forbidden because of his question." So I said: "I seek refuge with Allah from the anger of Allah and the anger of His Messenger." He (peace and blessings be upon him) raised his head and said: "What did you say?" I said: "Which jihad is best?" He (peace and blessings be upon him) said: "A word of justice before a tyrannical ruler."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14177