Tafsir of Al-Infitar 82:3

They are opened and their sides are split, such that the barrier between them is removed, the sweet water mixes with the bitter, and they become a single sea.

It is narrated that the earth will absorb the water after the seas have been filled, becoming level—meaning, without any water. It is intended that the seas will first become one, then the earth will absorb all of it, becoming devoid of water. It is also possible that what is meant by "leveling" after the drying up is that no depressions for water will remain, based on the words of the Exalted: "You will not see therein any crookedness or elevation."

Mujahid, al-Rabi’ ibn Khuthaym, al-Za’farani, and al-Thawri read fujirat (are made to gush forth) in the passive voice with the hardening of the jim (as a doubled consonant). From Mujahid, it is also narrated as fujirat (gushed forth) in the active voice, meaning they spring forth due to the disappearance of the barrier. The term fujur (gushing/wickedness) is considered in relation to the words of the Exalted: "neither of them transgresses," for transgression (baghy) and wickedness (fujur) are synonymous.