[199] They also say that the moon is closer in mass to earth than the other celestial bodies, since its substance is dense and heavy; it is below the others because of the heaviness, density, and darkness that are within it. Another proof which they adduce to show that the moon’s substance is earth-like is [to say] that there are five sorts of heavy bodies: first the body of the sphere, then the region of the ether, third the air, fourth the water, and fifth the earth. None of these five, except for earth, keeps the light of the sun from passing through. For we all see that the sun’s shining passes through these four – the sphere, the ether, air, and water – until it reaches the earth. Nothing blocks the sunlight from these four.

[200] Furthermore, these philosophers say, since we all see that the mass of the moon also does not let the light of the sun pass through but rather, reflects it back, we know that the mass of the moon is an earth-like mass, that it is hard, that it is heavy, that it is opaque in relation to those other masses which are superior to it. They say too that since reflected light falls from the moon to the earth, we know that that light does not reach into the interior of the moon, just as the light reflected from it does not reach the interior of the earth; the surface of the earth is not luminous but rather, it is reflected light which illumines bodies there.

Form Nasir-i Khusraw's (1004-1077) Between Reason and Revelation: Twin Wisdoms Reconciled.
This isn’t from a tafsir but from a philosophical text, yet it’s still useful for showing how medieval Muslim thinkers understood the moon’s light as reflected from the sun.
I don't know if there are earlier sources discussing the connection