Hadith: Fundamentals of Deen

Sayyiduna Abu Razin (RadhiAllaho anho) narrates
that Rasulullah (Sallallahu Alaihi Wasallam) said:

Should I not guide you to the fundamentals of Deen
by which you will obtain
the best of this world and the Hereafter?
Make it incumbent upon yourself to frequent
the gatherings of those who engage in Dhikr.
And when you are alone,
engage your tongue in the remembrance of
Allah as much as you can.

{Baihaqi, Mishkat}