5.3 (...) This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion.
But As we look at the topic of the completion of religion in the light of the whole Qur'an, we find that religion is described as being completed with regards to previous revelations than Quran, and not just Quranic Revelation. Every time God revealed a Religion, it was Perfected for its own time.
For instance, we find that God's favor was completed at the time of Abraham, Isaac, and Joseph:
And thus will your Lord choose you and teach you the interpretation of sayings and make His favor complete to you and to the children of Jacob, as He made it complete before to your fathers, Abraham and Isaac; surely your Lord is knowing, wise.
- Qur'an 12:6
We also find that God completed His favor through Moses:
Moreover, We gave Moses the Book, completing (Our favor) to those who would do right, and explaining all things in detail,- and a guide and a mercy, that they might believe in the meeting with their Lord.
- Qur'an 6:154
According to the Qur'an, the completion of the favor is also conditional upon the individual's success in obeying and fearing God:
And from whatsoever place you come forth, turn your face towards the Sacred Mosque; and wherever you are turn your face towards it, so that people shall have no accusation against you, except such of them as are unjust; so do not fear them, and fear Me, that I may complete My favor on you and that you may walk on the right course.
- Qur'an 2:150
Some argue however, that while "completion" of the favor may not be unique to Muslims, "perfection" of the religion is.
This is a matter of interpretation, and it certainly is the prerogative of the translators to have chosen the word "perfected" for the Arabic word "akmaltu". For Arabs (and others familiar with the language) however, while the word definitely conveys the meaning of perfection, and wholeness, it is also very often used to mean "completion" as we find in verses: 2:185, 2:196, 2:233, and 16:25 among others.
This same theme has also caused followers of other religions to believe that their religion was complete, not only for the duration it was destined, but for all times. For example we see that for the Christians, the favors of God were also completed on humanity through Jesus:
"And ye are complete in Him [i.e. Jesus] , which is the head of all principality and power"
- The Epistle to the Colossians, Chapter 2
"Epaphras, who is [one] of you, a servant of Christ, saluteth you, always labouring fervently for you in prayers, that ye may stand perfect and complete in all the will of God."
- The Epistle to the Colossians, Chapter 4
It is also necessary to remember, that both completeness and perfection are among God's attributes, integral to His Essence (magnified be His name). It would be blasphemous to doubt that any of His actions and doings or favors, would be anything but complete and perfect.
Therefore As it is revealed in Quran, each Age has its Book:
"Apostles truly have we already sent before thee, and wives and offspring have we given them. Yet no apostle had come with miracles unless by the leave of God.
To each age its Book."
ar-Ra`d 13:38
According to this verse Quran was a Book for its own Age, and is not the last Book.
Now we have to ask ourselves without denying the Reality:
Did the Worldwide Community of Muslims kept its unity and walked according to the Quran?
Lo! Ye are they, who are called to expend for the Cause of God: and some of you are niggards (stingy) but whoso is niggardly shall be niggard only to his own loss, for God is the rich and ye are the poor: and if ye turn back, he will change you for another people, and they shall not be your like!
Muhammad 47:38
Muhammad was asked who were the people He referred to as another people, who were to replace the Arabs? One of His famous followers, Salman Farsi, a Persian, was sitting near Him. Muhammad patted the legs of Salman and said: He and his people and He continued: By the True One, in Whose hands is My life, if the Faith of God should be suspended in the Pleiades, surely men from Persia shall reach it. (This tradition is accepted by Sunnis and Shiites and is included by Nasafi in his book, Vol 4, page 169, as well as by Muhammad Farid Vajdi, in his book, third edition, page 676)
Also Here:
The Life of Imam Abu Hanifah