The Prophet (saas) warned the People of the Book in the best way, and communicated to them, not a distorted, polytheistic form of religion, but rather Allah's final revelation. In the same way as with the disbelievers, the Prophet (saas) did not put pressure on the People of the Book, but simply conferred to them advice.
One of the main features of the People of the Book, and the Jews in particularly, is that they also see themselves as the dearest servants of Allah and claim that none but themselves can enter Paradise. Several verses in the Qur'an treat such a claim. The Qur'an reveals the answer given by the Prophet (saas) to that baseless assertion of theirs, which is unfounded:
When they are told, "Believe in what Allah has sent down," they say, "We believe in what was sent down to us," and they reject anything beyond that, even though it is the truth, confirming what they have. Say, "Why then, if you are believers, did you previously kill the prophets of Allah?" (Surat al-Baqara: 91)
Say, "If the abode of the hereafter with Allah is for you alone, to the exclusion of all others, then long for death if you are telling the truth." But they will never ever long for it because of what they have done. Allah knows the wrongdoers. (Surat al-Baqara: 94-95)
They say, "No one will enter the Garden except for Jews and Christians." Such is their vain hope. Say, "Produce your evidence if you are telling the truth." (Surat al-Baqara: 111)
The Jews and Christians say, "We are Allah's children and His loved ones." Say: "Why, then, does He punish you for your wrong actions? No, you are merely human beings among those He has created. He forgives whoever He wills and He punishes whoever He wills. The kingdom of the heavens and the earth and everything between them belongs to Allah. He is our final destination." (Surat al-Ma'ida: 18)
They say, "Be Jews or Christians and you will be guided." Say, "Rather adopt the religion of Ibrahim, a man of natural pure belief. He was not one of the idolators." (Surat al-Baqara: 135)
The Prophet (saas) also told the faithful to say, "Belief is to believe in Allah, His Angels, His Books, His Apostles…"63 when they talk to the people of the Book.