Sayyiduna Abu Hurairah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) used to stand (in prayer) for such a long time that his blessed feet would swell. It was said to him, "O Messenger of Allah, you undertake such a strenuous task, while Allah has already revealed to you that He has forgiven all your past and future mistakes?" The Prophet (peace and blessings be upon him) replied: "Should I not be a grateful servant?" These are the words of Muharibi’s narration. Imam Abu Bakr (may Allah have mercy on him) says that this hadith is evidence that gratitude to Allah is sometimes expressed through action, because all gratitude is for Allah alone. And sometimes gratitude is expressed verbally. The statement of Allah, the Exalted, is: «‏‏‏‏اعْمَلُوا آلَ دَاوُودَ شُكْرًا» ‏‏‏‏ [ سورة سبإ: 13 ] "O family of Dawud, work deeds of gratitude." Therefore, Allah has commanded them to perform righteous deeds as a form of gratitude to Him. Thus, gratitude is sometimes expressed through both speech and action. It is not as common people think, that gratitude is only expressed verbally. The words of the hadith, "Allah has forgiven all your past and future sins," are of the type about which I say that, linguistically, it is permissible to say "yakūn" (will be) in the meaning of "kāna" (has been). Because Allah, the Exalted, said to His Prophet (peace and blessings be upon him): «‏‏‏‏إِنَّا فَتَحْنَا لَكَ فَتْحًا مُّبِينًا» ‏‏‏‏ "Indeed, We have given you a clear conquest." And it was said to the Prophet (peace and blessings be upon him) that Allah has forgiven all your past and future sins, so the Prophet (peace and blessings be upon him) did not reject the statement, nor did he say that "My Lord has promised to forgive my sins," because He has already forgiven them.