The Islamic Creed In Summary.

[Abu Fauzi]

As-Salaam alaikum,
The briefest summary one may offer as the aqeedah in Islam is that whoever does not preserve the roots (usul) he or she will not arrive... meaning whoever does not follow the example of the Messenger of Allah, Sallallahu alaihi Wasallam, is prohibited from arriving.

What is meant by the roots is the Holy Qur'an and the Sunnah, that is the way of the Prophet alaihi salaat was-salaam. Thus everything that is performed, be it prayer, fasting.... their origin must be ascertained with the practices of the Noble Prophet, Sallallahu alaihi Wasallam...

[Ahmed.]

MaashAllah that's right

And I'll just add that it's our Scholars of our respective madhabs that 'ascertain' the sunnah for us as laymen won't be able to understand individual hadiths and Quranic ayahs in-depth and in context

[MazharShafiq]

yes it is necessary for complete imaan and will able to get jannah.