Tafsir of Al-Insan 76:19

(And there will circulate among them) for the purpose of service, (boys who are made eternal), meaning they are everlasting in the state they are in regarding freshness and splendor. It has been said that it means they are wearing khuldah, which is a type of earring. It is narrated in a hadith recorded by Ibn Marduyah on the authority of Anas, in a marfu' manner, that they are thousands of servants, and in some traditions, many times that.

The generosity is greater and the gifts are more expansive. This varies in scarcity and abundance according to the deeds of those being served. (If you saw them, you would think them scattered pearls) because of their beauty, the clarity of their complexions, the radiance of their faces, and their dispersion throughout their gatherings and dwellings, and the reflection of the light of some upon others. It has been said that they are likened to wet pearls when scattered from their shells because that is more beautiful and contains more luster. It is a simile of a singular object, as the dispersion is not the primary focus. The address in (If you saw them) is directed to the Prophet, may Allah exalt him and grant him peace, or to anyone who observes them; and the same applies to the words of the Exalted: