It is stated at many places in the Qur’ān that rivers will flow below Paradise. What exactly is the use of such rivers? How can they be counted as favour of God?
In order to understand the Qur’ānic description of Paradise, it may be noted that the Arabs of the times of the Prophet (sws) had a special taste regarding gardens. To them, the most scenic of gardens and orchards were those which were situated at some height above the ground level on some mountain or hill such that rivers and streams would flow around and beneath them at a lower altitude. The height not only adds to the beauty of the orchard, but also secures it from floods and similar calamities. Thus the words جَنَّاتٍ تَجْرِي مِنْ تَحْتِهَا الْأَنْهَارُ do not mean that the gardens of Paradise would have underground rivers. The word تَحْتِهَا (below it) here signifies a relative lower altitude of the rivers and not their being underground. The following verse portrays such a garden:
وَمَثَلُ الَّذِينَ يُنفِقُونَ أَمْوَالَهُمْ ابْتِغَاءَ مَرْضَاةِ اللَّهِ وَتَثْبِيتًا مِنْ أَنْفُسِهِمْ كَمَثَلِ جَنَّةٍ بِرَبْوَةٍ أَصَابَهَا وَابِلٌ فَآتَتْ أُكُلَهَا ضِعْفَيْنِ فَإِنْ لَمْ يُصِبْهَا وَابِلٌ فَطَلٌّ وَاللَّهُ بِمَا تَعْمَلُونَ بَصِيرٌ
And the likeness of those who spend their wealth, seeking to please Allah and to strengthen their souls is as a garden high and fertile: heavy rain falls on it but makes it yield a double increase of harvest, and if it receives not heavy rain, light moisture suffices it. Allah sees well whatever you do. (2:265)
At another place, the Qur’ān has mentioned the various types of الْأَنْهَارُ (rivers) that will flow in Paradise:
مَثَلُ الْجَنَّةِ الَّتِي وُعِدَ الْمُتَّقُونَ فِيهَا أَنْهَارٌ مِنْ مَاءٍ غَيْرِ آسِنٍ وَأَنْهَارٌ مِنْ لَبَنٍ لَمْ يَتَغَيَّرْ طَعْمُهُ وَأَنْهَارٌ مِنْ خَمْرٍ لَذَّةٍ لِلشَّارِبِينَ وَأَنْهَارٌ مِنْ عَسَلٍ مُصَفًّى
[Here is] a description of the Paradise which the righteous are promised: in it are rivers of water incorruptible; rivers of milk of which the taste never changes; rivers of wine, a joy to those who drink; and rivers of honey pure and clear. (47:15)