Tafsir of Al-Ghashiyah 88:12

Therein will be a running spring. meaning, flowing freely. This is mentioned with the intent of emphasizing affirmation. It is not intended to mean that there is only one spring. So here it refers to springs collectively. Thus, the meaning is that in it (Paradise) are flowing springs. Ibn Abi Hatim recorded from Abu Hurayrah that the Messenger of Allah said,

أنهار الجنة تفجر من تحت تﻼل أو من تحت جبال المسك

The rivers of Paradise spring forth from beneath hills -- or mountains -- of musk

فيها سرر مرفوعة