Sheikh `Abd al-Rahmân al-`Ajlân, lecturer at the Grand Mosque in Mecca
It is encouraged for a Muslim to engage in the remembrance of Allah as much as possible. Allah says: “O you who believe! remember Allah with much remembrance and glorify Him in the morning and evening.” [Sûrah al-Ahzâb: 41-42]
There are many other verses of the Qur’ân that convey the same meaning.
Also, the Prophet (peace be upon him) advised us to this by saying “Let your tongues remain moist with the remembrance of Allah.” [Sunan al-Tirmidhî (3375) and Sunan Ibn Mâjah (3793)]
However, it is not recommended to confine ourselves to the observance of a specific number of remembrances unless that is expressly indicated to us by the Prophet (peace be upon him).
For example, we have the remembrances which are recommended after the completion of prayer. We are to recite Subhân Allah thirty-three times, al-Hamdu Lillâh thirty-three times, and Allahu Akbar thirty-three times, then say once: La Ilâha illa Allah wahdahu lâ sharîka lah, lahu al-mulk, wa lahu al-hamd, wa huwa `alâ kulli shay’in qadîr.
We are also instructed to say Subhân Allah wa bi-Hamdihî one hundred times a day and La Ilâha illa Allah wahdahu lâ sharîka lah, lahu al-mulk, wa lahu al-hamd, wa huwa `alâ kulli shay’in qadîr one hundred times a day.
For such remembrances, we are to keep count of them and adhere to the prescribed number recommended by the Sunnah, using our fingers to keep count. For all other remembrances, we should recite them as often as possible without keeping count of them, not with our fingers, nor with stones or beads.
Source: Islam Today