As-Salaam alaikum,
The Noble Prophet, Sallallahu alaihi Wasallam, said: "There are 2 parts of the heart in one's body. In one part there lives an angel and in the other one there lives a devil. When a person remembers Allah, the devil stays away. And when one neglects the remembrance of Allah, the devil comes to stay in the heart and creates doubts for him."

He also, said, Sallallahu alaihi Wasallam, "The sign of love for Allah is dhikr (Zikr), and the sign of hatred against Allah is absence of dhikr." There is a Divine Saying (Hadith-Qudsi): "If you find My servant without dhikr, I interpose a curtain in between." Other sayings of the Prophet, alaihi salaat was-salaam, on this subject are:--

"The Remembrance of Allah brings knowledge of faith, makes one free of hypocrisy and becomes
a fort against Satan."

"There are 10 merits in the dhikr jalli (remembrance or invocation in the open): purity of heart,
warning against ignorance, physical health, battle against the enemies of Allah, expression of
faith, negation of the Satanic thoughts, negation of the lower nature, attention towards Allah,
turning away from other than Allah and lifting away the veil(s) between Allah and His Servant."

Source: 'Ain al-Faqr (The Spirit of al-Faqr), by Sultan Bahu.