Midrasch zu Kohelet 5:12

If thou lend money to any of my people (Exod. 22:24). Scripture says elsewhere in reference to this verse: There is a grievous evil which I have seen under the sun, namely riches kept by the owner thereof to his hurt; and those riches perish by evil adventure; and if he hath forgotten the sun, there is nothing in his hand (Eccles. 5:12–13). The Holy One, blessed be He, tests everyone; (with regard to) the wealthy, if they are generous toward the needy, they enjoy their wealth in this world, and the righteousness they perform will be rewarded in the world-to-come, as it is said: And thy reward (Isa. 58:8). It says elsewhere: Happy is he that considereth the poor; the Lord will deliver him in the day of evil (Ps. 41:2).

R. Chama, the son of R. Chanina, said: "Joseph hid three treasures in Egypt. One was revealed to Korah, and one to Antinones, the son of Asurius, and the third one is to be preserved for the righteous in the future [when Messiah will come] ." Resh Lakish said: (Ecc. 5, 12) "Riches reserved for their owner to his own harm, refers to the riches of Korah." (Deu. 11, 6) And all the existence that followed them. R. Elazar said: "This refers to the wealth of a man that puts man on his feet." R. Levi said: "Three hundred white mules were required to carry the keys of Korah's treasury, and all the keys and locks were made of white leather [so as to be of light weight]."

R. Chisda said: "He who quarrels with his master is considered as if he would quarrel with the Shechina, as it is said (Num. 26, 9) At the time they quarrelled against the Lord." R. Chama b. Chanina said: "He who murmurs against his master is considered as if he would murmur against the Shechina, as it is said (Ib. 20, 13) These are the waters of Meribah, where the children of Israel quarrelled with the Lord." And R. Chanina b. Papa said: "He who murmurs against his master is considered as if he would do so against the Shechina, as it is written (Ex. 16, 8) Not against us are your murmurings, but against the Lord." R. Abahu said: "Even one who meditates evil against his master is considered as if he meditates evil against the Shechina, as it is said (Num. 21, 5) And the people spoke against God and against Moses." (Eccl. 5, 12) Riches reserved for their owner to his own hurt. Resh Lakish said: "This refers to the riches of Korah." (Deut. 11, 6) And all … on their feet. R. Elazar said "This refers to their money which makes one stand on his feet." And R. Levi added: "The keys of Korah's treasure were of such weight that three hundred white mules had to carry them. All its keys and locks [usually of metal] were of leather [to make it easy to carry]."