We will answer your question through the following points:
1- We must keep in mind that all of the divine laws are based upon securing the interests of mankind and in keeping them away from harm. This means that nothing is lawful and unlawful without reason and it is not the case that things have been applied without any rhyme or reason.
2- It is worth mentioning that some of these reasons have been mentioned in a complete or partial manner in various Quranic verses and traditions. In some cases, it is also possible to learn of these reasons through an understanding of the spirit Islamic law in general and through other clues as well.
3- In some cases, if the reasons behind a divine ruling have not been explained, it is possible that the reason behind this is to cultivate a spirit of submission and obedience to the laws of God. This itself may be a reason behind the lack of an explicit explanation.
4- The human intellect is quite limited in its scope and cannot take grasp of each and every particular issue and its various facets and aspects. In the case that an individual cannot understand a divine ruling and the reasons behind it, it does not mean that the divine rules are without reason and that they should be rejected. The knowledge of God is unlimited in its scope, while the minute amount of knowledge that we possess is quite limited. It is important to keep in mind that each and every ruling is designed in the interests of mankind.
The question above will be answered through means of the following points:
1- All of the divine rulings were set with the interests of mankind in mind and it cannot be accepted that these rulings do not possess reasons behind their injunction. Anyone who has firm faith in the oneness of God and in His unlimited knowledge and power cannot doubt that all of the religious rulings and precepts in Islam were created with the interests of the people in mind. The wisdom and knowledge of God necessitates that He would not bring about any ruling which does not take into consideration the benefits of humanity.
Imam Riḍā (ʿa) has mentioned the following in a tradition: ‘Certainly, we have found the survival and interests of mankind in whatever God has made lawful (Ḥalāl); they are in need of such things and they cannot do without them. Likewise, we have found that mankind has no need of what (God) has made unlawful (Ḥarām); rather, such things are a cause of corruption for them which drives them towards annihilation and destruction.’
2- Although the human intellect is limited in its scope, still, certain reasons have been expounded upon in the verses of the Quran and in the traditions explaining various rulings and principles, as well as their effects. In some cases, these explanations are partial in scope, while in others they are comprehensive. For example, the book ʿIllal al-Sharāyiʿ by Shaykh Ṣadūq has detailed some of the philosophy, wisdom, and reasons behind certain religious rulings and principles and many related traditions have been narrated as well.
As an example, we will delve into the issue of prayer (Ṣalāt), which is one of the most important obligatory actions. Since God has not created man without a purpose and since man seeks completion and perfection intrinsically, he must have a means of reaching this perfection. This path is the path of servitude to God and obedience and it cannot be reached except through a state of awareness and consciousness. The opposite of awareness and consciousness is that of deviation and neglect and these are factors which prevent man from reaching perfection and nearness to God. Imam ʿAlī (ʿa) has mentioned the following: ‘Heedlessness is the deviation of the individual and it is the root of a variety of tribulations.’ One way of preventing such a state of heedlessness is that of the five daily prayers. Some of the effects of prayer, which have been mentioned, are those of putting a distance between man and the various unlawful actions and activities. The Holy Quran has mentioned the following about the prayer: “… and maintain the prayer. Indeed the prayer prevents indecencies and wrongs, and the remembrance of Allah is surely greater…”
3- It is possible that in some cases where God has not mentioned the reasons behind certain rulings, the lack of mention itself had a reason. Thus, the specific lack of mention was for the reason that God wished to strengthen the spirit of obedience in human beings. For example, if someone wishes to be a servant of God, do they really need to know why the morning prayer is 2 Rakats (units of prayer), while the noon prayer is 4? Should not knowing such a thing harm his faith in God? It is possible that the reason of not explaining such things is that God wishes to test the spirit of human beings and to strengthen their spirit of obedience and servitude. In such a case, an individual would tell themselves that they have faith in the wisdom of God and they know that God would not make something obligatory without reason. Therefore, they would submit to that order and perform that specific action without knowing the reasons behind why the morning prayer contains two rakats and the noon prayer contains four.
4- It is important to keep in mind that these divine rulings were given to the Prophets (ʿa) and the Imams (ʿa) from God in order that mankind may reach felicity and success, both in this world, as well as the next. If an individual cannot grasp the reason or philosophy behind a particular law, then he should not consider that law as being deficient and reject it. If someone were to do such a thing they would be trying to use their deficient intellect in order to understand something created by someone with a complete and unlimited intellect. If someone were to likewise go to a doctor for treatment of an illness and the doctor were to prescribe a cure, would a rational person ask the technical reasons behind such a prescription? And if the patient did not understand the reasons behind such a prescription should he simply discard it and assume it is without use?
In line with what we have just explained, it is acceptable to seek answers behind various religious precepts and to go after the wisdom behind such laws. Even though we have the right to ask such questions, it should not be expected that we will understand all the reasons due to the limited scope of our intellect and knowledge.
 Hurr Ameli, Muhammad ibn Hasan ibn Ali, Wasaa’il al-Shi’ah, vol. 25, pg. 51, hadith 31146, Aal al-Bayt (AS) Institute, Qum, first edition, 1409 AH.
 Agha Jamaluddin Khaansaari, Sharh Ghurar al-Hikam, vol. 1, pg. 369, Tehran University, first edition, 1987.
 Wasāʾil al-Shīʿah, vol. 4, p. 14 and 15.
 Surah ʿAnkabūt, Verse 45.