Accumulation and hoarding of wealth as mentioned in the following verses of Quran is the severest crime in Islam.
[3:180] let not those who withhold and hoard GOD's provisions think that this is good for them; it is bad for them. For they will carry their hoarding around their necks on the Day of Resurrection. GOD is the ultimate inheritor of the heavens and the earth. GOD is fully cognizant of everything you do.
[4:37] The ones who are stingy, exhort the people to be stingy, and conceal what GOD has bestowed upon them from His bounties. We have prepared for the disbelievers a shameful retribution.
[9:34]. Those who hoard the gold and silver, and do not spend them in the cause of GOD, promise them a painful retribution.
[9:35] The day will come when their gold and silver will be heated in the fire of Hell, then used to burn their foreheads, their sides, and their backs: "This is what you hoarded for yourselves, so taste what you have hoarded."