Allah's statement,

إِنَّمَا أَمْوَالُكُمْ وَأَوْلَادُكُمْ فِتْنَةٌ وَاللَّهُ عِندَهُ أَجْرٌ عَظِيمٌ ﴿١٥﴾

Your wealth and your children are only a Fintah, whereas Allah! With Him is a great reward.

Allah said that the wealth and children are a test and trial from Allah the Exalted for His creatures, so that He knows those who obey Him and those who disobey Him.

Allah's statement,وَاللَّهُ عِندَهُ (whereas Allah! With Him),

meaning, on the Day of Resurrection,أَجْرٌ عَظِيمٌ (is a great reward).

As Allah said;

زُيِّنَ لِلنَّاسِ حُبُّ الشَّهَوَتِ مِنَ النِّسَآءِ وَالْبَنِينَ وَالْقَنَـطِيرِ الْمُقَنطَرَةِ مِنَ الذَّهَبِ وَالْفِضَّةِ وَالْخَيْلِ الْمُسَوَّمَةِ وَالأَنْعَـمِ وَالْحَرْثِ ذَلِكَ مَتَـعُ الْحَيَوةِ الدُّنْيَا وَاللَّهُ عِندَهُ حُسْنُ الْمَأَبِ

Beautified for men is the love of things they covet; women children, Qanatir Al-Muqantarah of gold and silver, branded beautiful horses, cattle and well-tilled land. This is the pleasure of the present world's life; but Allah has the excellent return with him. (3:14), and the Ayah after it.

Imam Ahmad recorded that Buraydah said,

"The Messenger of Allah was giving a speech and Al-Hasan and Husayn came in wearing red shirts, walking and tripping. The Messenger descended from the Minbar, held them and placed them in front of them and said,

صَدَقَ اللهُ وَرَسُولُهُ

إِنَّمَا أَمْوَالُكُمْ وَأَوْلَادُكُمْ فِتْنَةٌ،

نَظَرْتُ إِلَى هَذَيْنِ الصَّبِيَّيْنِ يَمْشِيَانِ وَيَعْثُرَانِ، فَلَمْ أَصْبِرْ حَتْى قَطَعْتُ حَدِيثِي وَرَفَعْتُهُمَا

Allah and His Messenger said the truth,

`Verily, your wealth and your children are a Fitnah.'

I saw these two boys walking and tripping and could not be patient until I stopped my speech and picked them up.''

This was recorded by the Sunan compilers, and At-Tirmidhi said, "Hasan Gharib.''