Whoever hides sincere advice from the Muslims has acted deceitfully towards them

point 79: It is not permissible to hide sincere advice from any of the Muslims, whether pious or impious, in matters of the religion. Whoever hides that has acted deceitfully towards the Muslims. Whoever acts deceitfully towards the Muslims has done so towards the religion. Whoever acts deceitfully towards the religion has behaved treacherously towards Allah, His Messenger and the Believers [1]
[1] Tameem ad-Daaree narrates: The Messenger of Allah (sallallaahu alaihi wa sallam) said, “The religion is sincerity.” Upon this, we (the companions) asked, “To whom?” He (sallallaahu alaihi wa sallam) replied, “To Allah, His Book, His Messenger and to the leaders of the Muslims and their common folk.” Reported by Muslim (Eng. trans. 1/37/no.98).