Here "in their hand" stands for what they own. AT: "that were in their possession" or "that they had" (See: [[rc://en/ta/man/translate/figs-metonymy]])
"their earrings." Possible meanings are 1) the gold in the earrings could have been used to make more idols or 2) they took these earrings from the city of Shechem after they attacked it and killed all the people. The earrings would have reminded them of their sin.