Why should Allah be feared when living under the belief that Allah is loving and to love Allah can be more beneficial?

In the Name of Allah, Most Gracious, Most Merciful.

All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.

As servants of Allah, we must entertain love and hope in Allah with fear of His wrath, for Allah is Most Merciful and Compassionate and He is also Stern in punishment. Fear alone, without hope, is not recommended, just as hope alone, without fear, is not recommended.

The ideal way is, therefore, to combine fear of Allah with hope in His mercy.

We must fear Allah in such a way that we are prompted to avoid the things that incur His wrath; while we must entertain hope in Allah’s mercy in such a way that we must never hesitate to repent and change ourselves in order to receive the mercy of Allah.

You are right in saying that we must love Allah, but at the same time it is wrong to suggest that love of Allah excludes fear of Him. For while we are to love Allah unconditionally, we must also be afraid of incurring His wrath. This is because of the fact that just as Allah, the Most Exalted and Glorious, is the Compassionate and Merciful, He is also the Just and Stern in punishment.

If we wish to delve deeper in to this issue, we must clarify the following:

The issue of love of Allah is not so much a matter based on reason and logic; it is, rather, something based on revelation, for the way to approach Allah is dictated by revelation and not by pure reason. It is Allah and Allah alone Who must teach us how to approach Him. Otherwise, we are simply comparing Allah with His creation, and thus we end up shaping Allah in our own mind. Therefore, there is no way for us humans to know about Allah’s nature except through His own revelation.

Allah tells us about His nature in the Qur’an: (Tell My servants that I am the Forgiving, the Compassionate, and that My torment is indeed the painful torment) (Al-Hijr 15: 49–50). And in another place, Allah describes Himself as follows: (Allah, the Mighty, the Knower, the Forgiver of sins, the Acceptor of repentance, the Stern in punishment, the Bountiful. There is no deity beside Him. To Him is the final journey.) (Ghafir 40: 2–3).

Revelation tells us that as servants of Allah we must entertain love and hope of Allah with fear of His wrath, for Allah is Most Merciful and Compassionate and He is also Stern in punishment. Fear alone, without hope, is not recommended, just as hope alone, without fear, is not recommended.

The ideal way is, therefore, to combine fear of Allah with hope in His mercy. This, according to the Qur’an, is the way of prophets, the ideal role models for humanity. (They used to hasten to do good works, and called upon Us with hope and fear, and they were humble before Us) (Al-Anbiya’ 21: 90).

We must fear Allah in such a way that we are prompted to avoid the things that incur His wrath, while we must entertain hope in Allah’s mercy in such a way that we must never hesitate to repent and change ourselves in order to receive the mercy of Allah.

It is also possible to explain this rationally, for it is not hard to reason that every earnest and sincere lover must also be afraid of displeasing his or her beloved, and hence he or she will be careful not to say or do things that may directly or indirectly earn his or her anger.