Is it necessary, in achieving justice between wives, to provide equality in kind, or is it sufficient to meet the essential needs of each, such as giving money on Eid?

The justice obligatory upon a husband towards his wives is to equalize between them in terms of division (of time), expenditure, clothing, and sustenance. If the husband fulfills this, then he may prefer one of them over another as he wishes, according to the majority of scholars. What is meant by justice is equalizing between them in a manner befitting each of them. So, if he provides each of them with her clothing, expenditure, and shelter, then any additional inclination of the heart or offering of a gift will not harm him.