Belief in and worship of God requires on the part of a believer deep concern with creatures, animate or inanimate. The deeper one's belief in and submission to God is, the deeper one's concern for all creatures. Belief in the Unity of God allows no one on the earth to enjoy and exercise absolute freedom in dealing with creatures.
Islam, being a word derived from the root SLM, meaning salvation and peace as well as submission, is the expression of God's grace flowing in the arteries of the universe. Islam being the Divine system to which all creatures except man have willingly submitted themselves, there is no disorder observed throughout the universe. That is why Islam is, first of all, the religion of the universe. Everything in the universe is 'Muslim' for it obeys God by submission to His laws. Even a man who refuses to believe in God, or offers his worship to someone or something other than God, has perforce to be a Muslim as far as his bodily existence is concerned. For his entire life, from the embryonic stage to the body's dissolution into dust after death, and every tissue of his muscles and every limb of his body follow the course prescribed for each by God's law.
The principle of Tawhid (Divine Unity) in Islam implies the necessity of man's being in harmony with the world around him. The vast realm of the universe, which is in submission to One God only, displays a coherence and harmony of which the human world is also a part. Although the human world is subject, in addition to the general laws of nature, to a particular set of laws special to itself, yet it is also in harmony with other laws governing the rest of the phenomena beyond it. Man, unlike his fellow creatures who tread 'the path of nature', is endowed with the power of free will. He carries the gift of freedom together with the obligation to harmonize his life with the rest of nature – a harmony which is also the path of his exaltation and progress. This is the path upon which God has originated the nature of mankind:
Set your face to the religion, a man of pure faith – God's original nature in which He originated mankind. There is no changing God's creation. That is the right religion, but most men know it not. (al-Rum, 30.30)
Islam is the universal order, the integral religion of harmony and the unique system which is able to harmonize the physical with the metaphysical, the rational with the ideal, and the corporeal with the spiritual. All dimensions of man's earthly life have particular places of their own within the matrix of Islam in such a way that each can perform its own function and enable man to be at peace with himself, his community and nature, and ultimately to gain happiness in both worlds.
In order to be able to harmonize his life with the rest of nature, man should, first of all, realize his own personal integrity. This requires his application of his free will to his energies to keep them within the correct limits established by God. If he does not recognize any limits to his desire, he may, for example, usurp the property of others, seek illicit sexual relations, and so on. If, again, he does not recognize any limits to the use of his intellect, he may exploit it to deceive others. That is why man's powers must be held in check: his intellect must be exercised with 'wisdom', and his desire and anger restrained by lawfulness and moderation. We should remember too that man is a social being; if he does not restrain himself as demanded by God, certainly wrongdoing, injustice, exploitation, disorder and revolutions will occur in society.
God does not approve wrongdoing and disorder. He wills that human beings should live in peace and, accordingly, that justice should prevail amongst them. It is, therefore, incumbent upon those who believe in One God and worship Him faithfully to secure justice in the world. Islam calls this responsibility jihad, a term which can be rendered in English the best as struggle or, as some call it, the holy struggle in the way of God.