What is the significance of Dhikr in Islam?
Assalamualaikum! أَلَا بِذِكْرِ اللَّهِ تَطْمَئِنُّ الْقُلُوبُ (Indeed, in the remembrance of Allah do hearts find rest)
The best dhikr is "La ilaha illa Allah" (There is no deity worthy of worship except Allah).
Sources: Quran 13:28