The ruling didn't, and couldn't given the ICJ’s jurisdiction, order Hamas to do anything: https://news.ycombinator.com/item?id=39149823

> Hamas has previously claimed they would abide by any ruling of the court

No, Hamas previously claimed that they would observe a ceasefire if the court imposed one on Israel, conditioned on Israeli compliance with the same. They didn't say they would do anything related to anything other than an ceasefire order.