You know why Jesus was sent to the Jewish people? because they abandoned the Torah in favor of the oral laws (early Talmud, Mishnah) !
You know why following any other book than God's is condemned? because it is actually declaring Satan a god besides God.
You know what is common between the Muslims, the Christians and the Jewish now? They all have human idols, the Rabbis, Jesus and Muhammad. Their idols (willingly or unwillingly) have instituted man-made laws for them instead of God's!
When God says wash your hands before praying and then the Rabbi or the Sheikh says wash them three times, he, in this seemingly harmless utterance, has made himself a god besides God!, if he attributes this 'new' law to a dead prophet or saint then he has added to his sins by lying and all those who 'accept' this new law blindly without questioning are idolizing this human idol and are destined to Hell as idol-worshipers, unless they repent.
We think it is a small issue, yet it is the very issue that will determine our destiny.
I am sorry to say that, but the retribution when it comes will not discriminate, it will strike anybody who follow a law not authorized by God.
[6:112] We have permitted the enemies of every prophet - human and jinn devils - to inspire in each other fancy words, in order to deceive. Had your Lord willed, they would not have done it. You shall disregard them and their fabrications.
[6:113] This is to let the minds of those who do not believe in the Hereafter listen to such fabrications, and accept them, and thus expose their real convictions.
[6:114] Shall I seek other than GOD as a source of law, when He has revealed to you this book fully detailed? Those who received the scripture recognize that it has been revealed from your Lord, truthfully. You shall not harbor any doubt.
[3:64] Say, "O followers of the scripture, let us come to a logical agreement between us and you: that we shall not worship except GOD; that we never set up any idols besides Him, nor set up any human beings as lords beside GOD." If they turn away, say, "Bear witness that we are submitters."