What is the ruling on the fast of gratitude and the charity of gratitude?

There is no fasting of gratitude or prayer of gratitude in Islamic law. Whoever introduces them has innovated in religion something that does not belong to it. What is mentioned in Islamic law is the prostration of gratitude (sujud ash-shukr) upon the occurrence of a blessing or the removal of an affliction. There is no objection to increasing good deeds as an expression of gratitude to Allah Almighty for His blessings, as the Prophet, peace and blessings be upon him, did when he stood praying until his feet swelled, and he said: "Should I not be a grateful servant?"