How should a husband divide the rotation of nights between his wives?

The husband must divide the nights equally, for example one night for each wife in turn.
In the Shafi'i school, the basis of the rotation (qasm) is the night for one who works during the day; the day follows its night. The rotation may be one, two or three nights for each wife provided it is equal. A rotation of more than three nights each requires the wives' consent according to the authoritative view. The first cycle is begun by drawing lots or by mutual agreement so that no wife feels given precedence. What is obligatory is spending the night together (mabit), not necessarily intimacy. See Fiqh of polygyny and Managing the rotation.