Tafsir of Al-Waqi'ah 56:76

"And indeed, it is an oath—if you could know—[that is] mighty."

This [verse] contains a parenthetical clause within another, as the saying of the Exalted, "Indeed, it is an oath—[that is] mighty," is inserted between the oath and that which is being sworn to, which is His [Almighty's] saying: [The following verse].