Hazrat Shaikh Moulana Muhammad Zakariyya (rahmatullahi ‘alaih) writes:

It is a common observation and a fact proven through experience that man, regardless of how much wealth he may acquire, never remains satisfied and content with his lot. With the exception of a few blessed servants of Allah Ta‘ala, this is the general condition of man. It is for this reason we find that earnest exhortation and encouragement towards contentment is given in various places of the Holy Quraan and ahaadeeth. This is essential so that man’s insatiable appetite for wealth be curbed to some extent. (Fazaail-e-Sadaqaat [urdu], Part 2 –pg.369)

Source: Ihyaauddeen.co.za