question #1 Sahih Muslim 38, Book 1, Hadith 66 : What is the significance of affirming one’s faith in Allah in Islam?

I asked the Messenger of Allah to tell me about Islam a thing which might dispense with the necessity of my asking anybody after you. In the hadith of Abu Usama the (words) are: other than you. He (the Holy Prophet) remarked: Say I affirm my faith in Allah and then remain steadfast to it.