Sufyan bin 'Abdullah Ath-Thaqafi said: I said: "O Messenger of Allah! Inform me about a matter that I may hold fast to." He said: “Say: My Lord is Allah, then be steadfast.' I said: "O Messenger of Allah! What do you fear most for me?" So he took hold of his tongue and said: “This””
SahihSahihHasan SahihBook 36 · Hadith 108