What does this statement, "Surely thou didst so little contribute to this great kingdome . . . cave and grot," mean?
In this poem, Herbert creates an extended metaphor (conceit) about how money is the root of all evil. Herbert personifies evil and this makes the conceit more effective because he/speaker can blame this personified money. He says that money came from poor parents and this means that money such as gold came from the earth, the dirt, or a mine. While he blames "money" for causing so much suffering, he adds that it is actually humans who have made money rich and powerful. Therefore, any evil that results from money is actually the fault of humanity. Money is an inanimate thing. It is as foolish to blame money itself as it is to praise money for its worth. Herbert is criticizing people for praising money instead of praising God.
In the second stanza, the speaker notes that money did little (or nothing) to contribute to God's kingdom. But, since humans have given money so much power, money seems to own the kingdom. Humanity was "fain" (pleased) when they dug money out of the cave and "grot" (ground or cavern). Man (humanity) has dug money out of the dirt and made it valuable. Herbert concludes the poem with the statement that digging money out of the ground, making it valuable and then praising it is a path towards destruction:
Man calleth thee his wealth, who made thee rich;
And while he digs out thee, falls in the ditch.