The Virtues of the Dhikr
The Messenger of God (peace and blessings be upon him) said: "There are two phrases which are light on the tongue, heavy on the scale, and beloved to the Most Merciful Allah." These phrases are Subḥānallāh (glory be to Allah, declaring Him free from all imperfection; see first occurrence: tawhid [the oneness of God]) and al-ḥamdu lillāh (all praise is due to Allah).
Dhikr That Is Light on the Tongue, Heavy on the Scale
"There are two phrases which are light on the tongue, heavy on the scale, and beloved to the Most Merciful Allah:
سُبْحانَ اللّٰهِ وَبِحَمْدِه۪ سُبْحَانَ اللّٰهِ الْعَظِيمِ
I declare Allah free from all attributes unbefitting His divinity and praise Him. I again declare the Mighty Allah free from all attributes unbefitting His divinity." (Bukhārī, Daʿawāt 65, Aymān 19, Tawḥīd 58; Muslim, Dhikr 31)
Allah, exalted is He, wills that His servant’s heart be with Him at every moment. As stated in the verse (āya): "They remember Allah while standing, sitting, and lying on their sides" (at all times) …" (Āl ʿImrān, 191). In the aforementioned ḥadīths, the virtue and the great reward of this glorification (tasbīḥ) are expressed. This is, in a sense, for encouragement and motivation. Therefore, we should not confine the remembrance of Allah (dhikr) to only this glorification, but, in accordance with the requirements of the verses (āyāt) and ḥadīths, it is necessary that we be in a state of constant remembrance (dhikr-i dāʾim).