Can a Muslim who performs a simple good deed attain Firdaus if he asks Allah for it, based on the saying of the Prophet, peace and blessings be upon him: "If you ask Allah for anything, then ask Him for Firdaus, for it is the highest part of Paradise and from it gush forth the rivers of Paradise"?

The hadith (definition) about asking for the highest Paradise (al-Firdaws al-A'la) is authentic, and we must believe in it and follow the Prophetic guidance. Supplication is an act of worship, and Allah the Almighty says: "Call upon Me; I will respond to you." Entering Paradise is not in exchange for deeds, but deeds are a cause, as stated in the hadith: "None of you will be saved by his deeds except that Allah encompasses me with His mercy and grace." The verse "Enter Paradise because of what you used to do" means "because of your deeds," for a person's deeds cannot compensate for even the simplest of Allah's blessings. A small deed or a simple word can be a reason for attaining the highest Paradise, an example of which is the story of the man who watered a dog, and Allah forgave him. A Muslim should ask Allah for the highest Paradise, for supplication itself is a deed, and success is in Allah's hands.