A true servant of God aspires to remember God every moment of the day, with each and every breath. The Zikr, the repetition of the name of God, is the fundamental practice of remembrance of God in Islam.
Say: ‘Allah.’ Then leave them alone, playing their game of plunging. [Quran 6:91]
Prophet Muhammad (peace and blessings be upon him) said “There is a polish for everything that taketh away rust; and the polish of the heart is the remembrance of Allah”. Jalal ad Din Rumi said “Remembrance makes people desire the journey: it makes them into travellers.” Kabir expressed zikr beautifully “The breath that does not repeat the name of Allah is a wasted breath.” Shaykh Abdur Qadir Jilani used to say “Truth (Haqq) has been planted in the center of the heart as the trust (amanat) of Allah, entrusted to you for safekeeping. It becomes manifest with true repentance and with true efforts. Its beauty shines on the surface when one remembers Allah and does the Zikr. At the first stage one recites the name of Allah with one’s tongue; then when the heart becomes alive one recites inwardly with the heart.”
Once Sahl al Tustari said to one of his disciples: “Try to say continuously for one day: ‘Allah! Allah! Allah!’ and do the same the next day and day after, until it becomes a habit.” Then he told him to repeat it at night also, until it became so familiar that the disciple repeated it even during his sleep. Then Sahl said, “Do not consciously repeat the Name any more, but let your whole faculties be engrossed in remembering Him!” the disciple did this until he became absorbed in the thought of Allah. One day, a piece of wood fell on his head and broke it. The drops of blood that dripped to the ground bore the name, “Allah! Allah! Allah!”
In another interesting tale appearing in Jalal ad Din Rumi’s matsnavi, “A devotee was praying when Satan appeared to him and said: “How long wilt thou cry ‘O Allah?’ Be quiet for thou wilt get no answer.” The devotee hung his head in silence. After a while he had a vision of the Khidr, who said to him, “Ah, why hast thou ceased to call on Allah?” “Because the answer, ‘Here I am,’ came not,” he replied. Khidr said, “Allah hath ordered me to go to thee and say this: ‘Was it not I that summoned thee to My service? Did I not make thee busy with My name? Thy calling “Allah!” was my “Here I am,” Thy yearning pain My messenger to thee. Of all those tears and cries and supplications I was the magnet, and I gave them wings.”
In hadeeth Qudsi God says “I am the companion of him who remembers Me.” “Whoever remembers Me in his heart, I remember him in myself, and whoever remembers Me in an assembly, I remember him to an assembly better than his own.”
Sahl al Tustari would say “Not a day passes but that the Allah Exalted cries out, “O my servant, you treat me unjustly. I remember you, but you forget Me. I invite you to Myself, but you go to others.”