What is the authenticity of the Hadith that mentions a supplication, which if recited, a year would pass and the angels would not be able to finish recording the good deeds of its reciter, and it is: "There is no god but Allah as many times as there has been, and as many times as there will be, and as many times as there are movements and stillness"?

There is no harm in reciting this dhikr (remembrance), but there is no evidence to prove its authenticity, the reward associated with it, or what the angels said. This is because matters concerning angels and rewards belong to the realm of the unseen, which requires pausing until they are substantiated. It has been authentically reported that the Prophet (peace and blessings be upon him) said to Juwayriyah: "I have said four words three times after you that, if weighed against what you have said today, would outweigh them: 'Subhanallah wa bihamdihi, adada khalqihi, wa rida nafsihi, wa zinata arshihi, wa midada kalimatihi' (Glory be to Allah and praise be to Him, as much as the number of His creation, as much as pleases Him, as much as the weight of His Throne, and as much as the ink of His words)."