Tafsir of Ar-Rahman 55:66

In them (both) will be two springs Naddakhatan. There is no doubt that the former two gardens are better, their branches are fresh, youthful and intermingling. Allah said about the former two gardens,

فيهما عينان تجريان

(In them (both) will be two springs flowing (free)), while He said about the springs of the latter two gardens,

نضاختان

(Naddakhatan); Ali bin Abi Talhah reported from Ibn Abbas: "It means gushing. And the free flowing is stronger than gushing.'' Ad-Dahhak said that,

نضاختان

(gushing forth) means, they are full of water and constantly gushing

فبٲي آﻻء ربكما تكذبان