Endless greed of humans
Imam Ja'far Sadeq (as) says:
If the children of Adam possessed two vast lands full of gold and silver, they would still wish to search for a third one.
لَو أنَّ لِإبنِ آدَمَ وادِیَیْنِ یَسِیلانِ ذَهَباً وَفِضَّةً لَابْتَغَی…