A Maulana says that Nabi Haroon (Alayhis salaam) had made an error of judgment (ijtihaadi error) for having remained with Bani Israail when they worsh

Answer

Nabi Musa (Alayhis salaam) had expected Nabi Haaroon (Alayhis salaam) to have dissociated from Bani Israaeel when they refused to heed his Amr Bil Ma'roof Nahyi Anil Munkar.

This is the course of action to adopt when the Amr Bil Ma'roof is rejected. It is not permissible then to remain in the company of the flagrant sinners. Thus, Nabi Musaa (Alayhis salaam) rebuked Nabi Haaroon (Alayhis salaam). However, when he was apprized of the valid reason for Nabi Haaroon (Alayhis salaam) not having left the people, he (Nabi Musaa) accepted the veracity of the reason. Thus, Nabi Haaroon (Alayhis salaam) did not commit an ijtihaadi error. His remaining with the people was based on a valid reason.