Is whistling forbidden? And is whistling at night and talking in the bathroom among the acts of the devils?

Whistling and speaking unnecessarily while relieving oneself in the restroom are disliked. The dislike intensifies when both actions are combined, based on the Almighty's saying: "And their prayer at the House was nothing but whistling and clapping." [Al-Anfal: 35] And according to the Prophet, peace and blessings be upon him: "No two men should go out to relieve themselves, uncovering their 'awrahs and conversing, for indeed Allah, the Blessed and Exalted, is displeased with that." Exceptions are made for situations of necessity.