The wording presents them as two only because it mentions two attributes of a single thing. A similar example occurs in the words of Allah Most High:

“He has sent down to you the Book in truth, confirming what came before it, and He sent down the Torah and the Gospel previously, as guidance for mankind, and He sent down the Criterion.”

Qatāda and al-Rabī' said: “It is the Quran, in which He distinguished between the lawful and the unlawful, and between truth and falsehood.” This is because, when a single thing has two major attributes, considering one attribute presents it as one thing, while considering both gives it the standing of two. Indeed, if its attributes are numerous, it may have the standing of several persons. Do you not see that a man skilled in arithmetic and medicine is equivalent to both a calculator and a physician, while a man skilled in carpentry and building is equivalent to both a carpenter and a builder?

Since the heart receives remembrance and knowledge, it is like a vessel into which water is placed. In this line of verse, he specifically calls it a vessel, rather than using any of the heart’s other names, because a vessel can be delicate and clear, and because it is what someone seeking food and charity brings, in the position of a destitute pauper. Since the heart also turns away from falsehood, it is pure and sound. It is thus as though it were two things.

To make the vessel appear distinct from the heart in this illustration, he says:

When you place your heart where it does not belong—although it is where remembrance and knowledge are to be placed—and you have no vessel with you in which to receive what you seek, you are like a man who heard that a wealthy person was distributing food to people, and who had a bowl