Praise be to Allah, and may peace and blessings be upon the Messenger of Allah. To proceed:
Fearing Allah Almighty is a great act of worship, and it is one of the causes of a person’s righteousness and success. Allah Almighty says:
“So fear them not, but fear Me, if you are [indeed] believers.”
Aal ‘Imran: 175.
Praiseworthy fear is that which motivates a Muslim to obey Allah and refrain from disobeying Him, without leading him to despair or lose hope.
Should we fear those who do not fear Allah?
Fear of people should not be made equal to fear of Allah, and the statement “Fear Allah, and fear the one who does not fear Allah” should not be used without qualification, because Allah has commanded the believer to fear Him and place his trust in Him.
However, this does not prevent a Muslim from taking necessary precautions and being cautious of the harm of oppressive and corrupt people, without having in his heart the kind of fear and exaltation that belongs to Allah. Rather, the Muslim knows that harm and benefit are in the hands of Allah alone.
Allah Almighty says:
“And whoever puts his trust in Allah, then He is sufficient for him.”
At-Talaq: 3.
Conclusion
The obligatory fear is fear of Allah Almighty. As for people, they are not to be feared with the fear of worship or exaltation. Rather, one should be cautious of their harm, take appropriate precautions, and place one’s trust in Allah. Therefore, the statement “Fear Allah, and fear the one who does not fear Allah” is not correct when stated without qualification, and it is better to avoid using it.
And Allah knows best.