Between them is a barrier [so] they do not transgress.

Between them is a barrier: That is, a partition from the power of Allah the Exalted, or from the physical bodies of the earth, as Qatada said.

So they do not transgress: This means that neither of them transgresses against the other by intermingling and completely nullifying the [specific] property of the other, based on the first interpretation previously mentioned. Or, it means they do not exceed their limits by flooding what is between them, based on the second interpretation. This has also been narrated from Qatada.

In the same meaning is that which Abd al-Razzaq and Ibn al-Mundhir recorded from al-Hasan: "They do not transgress against you by drowning you." It has also been said: The meaning is that they do not seek a state other than the state upon which they were created and for which they were subjected.