And believe in what I have sent down (this Qur'ân), confirming that which is with you, [the Taurât (Torah) and the Injeel (Gospel)], and be not the first to disbelieve therein, and buy not with My Verses [the Taurât (Torah) and the Injeel (Gospel)] a small price (i.e. getting a small gain by selling My Verses), and fear Me and Me Alone. (2:41)

Allah is saying to those who are Jews, and Christians, who are called the people of the book. Allah is saying to all those that this Qur'an proves all past messages that came to numerous prophets, whether a small message or an entire book, such as the Injil, Taurah, or the Zaboor. 

Even today those who call themselves Muslims, but do not practice, and leave the Qur'an behind for worldly matters, law, and short success. As going after worldly unlimited education, while  leaving the laws of the Qur'an behind, and thinking that this world is a permanent place for them, and they leave behind the hereafter, which can approach anyone any second, regardless of label, such as, Jew, Christian, Muslim, or anyone else.

Allah is saying to bring Iman, meaning practicing laws which came from Allah, and not to listen to any religious leaders, testify to yourself if you are on the right path or not, any religious leader will not come or save you in your grave.

All the originally sent books, in there original form, untouched by any human being, because no one has any right to touch the message of Allah, for example, if one is a writer of a book, and people start to come and change that person's original idea, what is being focused in that book, and they start to show there smartness, and without that person's permission they change the book's wordings, then that would upset the author, the same thing applies with people who are constantly changing the Bible, and the Torah, and whatever is liked is kept, and if not, then they take it out, with the excuse that these things don't apply today and they are introducing new editions, and making the old editions obsolete in order to earn more from the public, this is mentioned in the Qur'an, and Allah knows what we conceal in our hearts up to the last day of this world, so they are trying to say that they are smarter than the creator. The original books are certified and testified in the Qur'an, once they read it carefully each law, sentence, or verse. They will find the same guidance that was sent to Abraham, Moses, Jesus, or any other Prophet, and Muhammed (S.A.W).

"...This day, I have perfected your religion for you, completed My Favor upon you, and have chosen for you Islâm as your religion. But as for him who is forced by severe hunger, with no inclination to sin (such can eat these above-mentioned meats), then surely, Allâh is Of Forgiving, Most Merciful..." (5:3)

To stop innovations in religions, Allah has sealed it in this verse, that he has completed the guidance and commands for mankind to follow. Meaning, there is no requirement at all for improvements, in the law for our lifestyle, because any law which is man-made always needs improvements, it is only the laws of Allah that never need improvements for those who are willing to apply and get benefits.

"fear Me and Me Alone." (2:41)

Good and bad comes from Allah, whenever anyone is in trouble, it is only Allah alone who can solve the problem, without any intercession from anyone. No human being has any power to tell Allah what to do, he is an independent power, and never seeks help from anyone and no one is equal to him, so we should always fear Allah only. Whoever does not fear Allah, then it means he or she is not connected with Allah, but with Satan. Because to fear Allah is the only way to make a person connected with Allah, because Allah has all controls and is the creator, provider, and sustainer for everything, and who has the will to stop any of these bounties anytime he wants, according to our behavior, the way we act, we are responded to in the same way.