Ar-Ra'd 13:26

Increase and Decrease in Provision is in Allah's Hand

Allah states that He alone increases the provisions for whom He wills and decreases it for whom He wills, according to His wisdom and perfect justice. So, when the disbelievers rejoice with the life of the present world that was given to them, they do not know that they are being tested and tried. Allah said in other Ayat,

أَيَحْسَبُونَ أَنَّمَا نُمِدُّهُمْ بِهِ مِن مَّالٍ وَبَنِينَ - نُسَارِعُ لَهُمْ فِى الْخَيْرَتِ بَل لاَّ يَشْعُرُونَ

(Do they think that in wealth and children with which We enlarge them. We hasten unto them with good things. Nay, but they perceive not.)23:55-56 Allah belittled the life of the present world in comparison to what He has prepared for His believing servants in the Hereafter,

وَمَا الْحَيَوةُ الدُّنْيَا فِى الاٌّخِرَةِ إِلاَّ مَتَـعٌ

(whereas the life of this world compared to the Hereafter is but a brief passing enjoyment.) Allah said in other Ayat,

قُلْ مَتَـعُ الدُّنْيَا قَلِيلٌ وَالاٌّخِرَةُ خَيْرٌ لِّمَنِ اتَّقَى وَلاَ تُظْلَمُونَ فَتِيلاً

(Say: "Short is the enjoyment of this world. The Hereafter is (far) better for him who has Taqwa, and you shall not be dealt with unjustly even equal to the amount of a Fatila.)4:77 and,

بَلْ تُؤْثِرُونَ الْحَيَوةَ الدُّنْيَا - وَالاٌّخِرَةُ خَيْرٌ وَأَبْقَى

(Nay, you prefer the life of this world, although the Hereafter is better and more lasting.)87:16-17 Imam Ahmad recorded that Al-Mustawrid, from Bani Fihr, said that the Messenger of Allah ﷺ said,

«مَا الدُّنْيَا فِي الْآخِرَةِ إِلَّا كَمَا يَجْعَلُ أَحَدُكُمْ إصْبَعَهُ هَذِهِ فِي الْيَمِّ، فَلْيَنْظُرْ بِمَ تَرْجِع»

(The life of the present world, compared to the Hereafter, is just like when one of you inserts his finger in the sea, so let him contemplate how much of it will it carry.) and he pointed with the index finger. Imam Muslim also collected this Hadith in his Sahih. In another Hadith, the Prophet passed by a dead sheep, whose ears were small, and said,

«وَاللهِ لَلدُّنْيَا أَهْوَنُ عَلَى اللهِ مِنْ هَذَا عَلَى أَهْلِهِ حِينَ أَلْقَوه»

(By Allah! The life of this present world is as insignificant to Allah as this sheep was to its owners when they threw it away.)

وَيَقُولُ الَّذِينَ كَفَرُواْ لَوْلاَ أُنزِلَ عَلَيْهِ ءَايَةٌ مِّن رَّبِّهِ قُلْ إِنَّ اللَّهَ يُضِلُّ مَن يَشَآءُ وَيَهْدِى إِلَيْهِ مَنْ أَنَابَ - الَّذِينَ ءَامَنُواْ وَتَطْمَئِنُّ قُلُوبُهُمْ بِذِكْرِ اللَّهِ أَلاَ بِذِكْرِ اللَّهِ تَطْمَئِنُّ الْقُلُوبُ - الَّذِينَ آمَنُواْ وَعَمِلُواْ الصَّـلِحَاتِ طُوبَى لَهُمْ وَحُسْنُ مَـَابٍ

Tafsir Ibn Kathir (abridged, English).