Each [of them] has the tanween as a substitute for the added noun, meaning: all of them are in a sphere swimming. The pronoun refers to the sun and the moon, and what is meant by them is the kind of celestial bodies that appear every day and night. They made them numerous due to the multitude of their appearances, which is the reason for gathering them with suns and moons. Otherwise, the sun is one and the moon is one. The pronoun is made to refer to rational beings due to their action, which is swimming. If you say: what is the position of the sentence? I say: its position is accusative as a description of the sun and the moon. If you say: how is it that they are singled out without the night and day in the accusative description of them? I say: as you would say: I saw Zayd and Hind adorned, and so on, when you bring a description that is specific to some of what the doer is related to. From this is His saying, exalted is He, in this surah: 'And We granted him Isaac and Jacob as a gift,' or it has no position due to its being an independent statement. If you say: each of the two moons has a separate sphere, how is it said: all of them swim in a sphere? I say: this is like saying 'the prince clothed them in a robe and adorned them with a sword,' meaning each one of them, or he clothed them and adorned them with these two kinds, so he sufficed with what indicates the kind for brevity, and because the purpose is to indicate the kind.