Is there any mention of a virtue for the remembrance: "There is no god but Allah; we worship none but Him" in the Prophetic Sunnah or from the Companions?

There is no authentic hadith specifically stating the complete phrase, "There is no god but Allah, and we worship none but Him." What has been reported concerning this from Al-Tabarani is a weak hadith.

However, it is authentically reported that the Prophet, peace and blessings be upon him, used to say after prayer: "There is no god but Allah, He is alone without partner. To Him belongs all sovereignty and all praise, and He is over all things competent. There is no might nor power except with Allah. There is no god but Allah, and we worship none but Him. To Him belong all blessings, all bounty, and all goodly praise. There is no god but Allah, sincere in devotion to Him, even if the disbelievers detest it."

The word of Tawheed (monotheism) holds immense virtue. It has been reported that if it were placed in one pan of a scale, it would outweigh the seven heavens and seven earths, and that it is the best form of remembrance (dhikr).