All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Codes of law have the same principal fundamentals but differ in some sub-essential issues. This situation is based on the Divine Will and learning of people's states of affairs on the one hand, and in accordance with the circumstances, status, way of thinking and extent of bearing such ordinances and commandments. That is why you find something in this Sharee’ah is forbidden while it was lawful in a previous legislation; something is mandatory here and optional there. It is only Allah Who knows the wisdom. You may find that burdens are laid down on a nation; i.e. in the Sharee’ah that was sent to them. Only Allah knows the secrets and wisdom of such a situation. This may be a result of some nation's disobedience and defiance to the Divine Commandments and the Prophetic Sunnah.
Allah Says (what means): {For wrongdoing on the part of the Jews, We made unlawful for them [certain] good foods which had been lawful to them, and for their averting from the way of Allah many [people], And [for] their taking of usury while they had been forbidden from it, and their consuming of the people's wealth unjustly. And we have prepared for the disbelievers among them a painful punishment….} [Quran 4:160-161]
The above-mentioned verse states that Allah, The Great and Al-mighty, has forbidden the Jews certain wholesome things because of their wicked actions.
Since our Prophet, Muhammad is the last of Allah's Prophets and Messengers and their leader, the Sharee’ah of Islam comes to be the most complete one, suitable both for worldly and religious interests of all peoples, in all places and at all times.
The Quran and Hadeeth state clearly and precisely that the Prophet Muhammad is Allah's Messenger to the Jinn and Mankind.
Allah Says (what means): {Say, [O Muhammad], “O mankind, indeed I am the Messenger of Allah to you all, [from Him] to whom belongs the dominion of the heavens and the earth. There is no deity except Him; He gives life and causes death.” So believe in Allah and His Messenger, the unlettered prophet, who believes in Allah and His words, and follow him that you may be guided.”} [Quran 7:158]
This above-verse presents a clear evidence that Muhammad's message is a mundane and universal message.
Allah also Says (what means): {And We have not sent you except comprehensively to mankind as a bringer of good tidings and a warner. But most of the people do not know…} [Quran 34:28]
Allah further Says (what means): {Blessed is He who sent down the Criterion upon His Servant that he may be to the worlds a warner.} [Quran 25:1]
Besides, Jabir reported that the Prophet said: “Every Prophet was sent to his nation only and I have been sent to all nations.”
Another Hadeeth by Abu Moosa al-Ash'ari reads: “I swear by Him in Whose Hand my soul is, there is no Jew or Christian of this nation (of people from the time of the Prophet, until the Day of Judgment) who hears about me and then dies without believing in what I was sent with, except that he will be amongst the people of Hellfire.” [Muslim]
This Hadeeth states clearly that the message of Islam is for all mankind and that Muhammad is the last Prophet.
Islam presents the complete Sharee’ah and Muslims are the best nation if they commit to Islam in word and in deed.
Allah Says (what means): {You are the best nation produced [as an example] for mankind. You enjoin what is right and forbid what is wrong and believe in Allah.} [Quran 3:110]
Allah also Says (what means): {This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion.} [Quran 5:3]
This means that every nation had a Sharee’ah that was suitable for it for some fixed period of time, but Islam comes to be the most complete Sharee’ah for all nations, in all places and at all times. Islam is a code of life that organizes the human affairs in all walks of life till the Day of Judgment. In addition, since Prophet Muhammad is the last Messenger, all previous Divine Books informed of his coming.
Allah knows best.