Say 'I believe in Allah' and then be Steadfast

On the authority of Abu ’Amr — and he is also called Abu ’Amrah — Sufyan bin Abdullah ath- Thaqafee(ra) who said:

I said, 'O Messenger of Allah, tell me something about al-Islam which I can ask of no one but you.'
He (sas) said, Say I believe in Allah — and then be Steadfast. [Bukhari]