Say I believe in Allah and then adhere to steadfastness
On the authority of Abu `Amr — and he is also called Abu `Amrah — Sufyan bin Abdullah ath- Thaqafee (may Allah be pleased with him) who said:
"I said, "O Messenger of Allah, tell me something about al-Islam which I can ask of no one but you." He, peace and blessings of Allah be upon him, said, "Say I believe in Allah and then adhere to steadfastness." [Muslim]
A sign of man's good observance of Islam is his keenness to understand the rulings of his religion than his concern on the worldly affairs; since he knows that committing to Islam is the way to salvation, and the sound way of living in this world.
This great companion has become a Muslim after the battle of Hunain. He is determined to establish his religion on fixed foundations that are not difficult to understand, and are not too hard for him to memorize. He went to the one on whose tongue the springs of wisdom burst, and asked him for a concise statement that encompasses the foundations and branches of Islam, so that he takes it as an approach and a light to guide him in the way to Allah Almighty, after which he does not need to ask anyone else concerning the matters of his religion, As he knows that the Messenger of Allah, peace and blessings of Allah be upon him, has been granted the all inclusive words, therefore, it is not difficult for him to summarize Islam for him in a few memorable words.