All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
Fearing dogs or fearing the night is not forbidden because this is a natural fear, and the person who fears this is not considered as committing Shirk [associating partners with Allaah]; for more benefit, please refer to Fatwa 92486.
However, this fear should not lead a Muslim to have whispers and bad thoughts which may lead to unpleasant consequences or to neglect some religious obligations, in which case this is a dispraised fear.
Therefore, a Muslim may repel this fear by seeking the Help of Allaah and remembering that everything is in His Hands. Allaah Says (what means): {And upon Allaah rely, if you should be believers.}[Quran 5:23]
Concerning the devil, he also cannot harm anyone except by the Will of Allaah because he is weak as Allaah informed us in His Book. Therefore, if you feel any fear from him, then mention the Name of Allaah and say “A’oothu Bi Kalimaati Allaahi At-Taammaati Min Sharri Ma Khalaq.” (I seek refuge in Allaah’s perfect Words from the evil that He has created.), and say ‘La hawla wa la quwwata illa billaah’ (There is no might nor power except with Allaah). Moreover, you should remember the Saying of Allaah which means: {Say, “Never will we be struck except by what Allaah has decreed for us; He is our protector.” And upon Allaah let the believers rely.}[Quran 9:51] Besides, you should reserve a time for reciting and pondering over the Book of Allaah as it contains mercy and cure for what is in the chests of people. Finally, we advise you to recite the morning and evening legislated mention of Allaah and the confirmed supplications from the Prophet at different times.
Allaah Knows best.