Tafsir of Al-Waqi'ah 56:16

(Reclining upon them) is a state for the pronoun contained within the prepositional phrase, meaning: upon thrones.

And His saying, the Exalted: (Facing one another)

is also a state for it [the pronoun]. You may also consider the two states to be overlapping. The intended meaning, as Mujahid said, is: none of them looks at the back of his companion. This is a description of them regarding the excellence and refinement of character, the observance of etiquette, and the purity of their inner selves.