If it is asked: What is the proof that in his era there were people belonging to this Inward religion? We say: the proof of that is the saying of the Exalted in Surah al-Nisa: {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. But those firm in knowledge among them and the believers believe in what has been revealed to you, [O Muhammad], and what was revealed before you. And the establishers of prayer and the givers of zakah and the believers in Allah and the Last Day - those We will give a great reward.} (An-Nisa 160-162)

Contemplate the saying of Christ: "You have heard that it was said: An eye for an eye and a tooth for a tooth. But I say to you: do not resist the evil person, but whoever slaps you on your right cheek, turn the other to him also..."

This indicates that some of the sayings of the revealed books were interpreted by people according to their own opinions, far from what Allah the Exalted intended.