Is it permissible for a Muslim to describe Christians or Jews as Kafirs (disbelievers)?
It is permissible for a Muslim to describe the Christians or Jews as Kafirs based on the description they were given in the Qur'an. Whoever ponders the related Qur'anic Ayahs becomes aware of this fact. Allah (Exalted be He) says,
Verily, those who disbelieve (in the religion of Islâm, the Qur’ân and Prophet Muhammad صلى الله عليه وسلم) from among the people of the Scripture (Jews and Christians) and Al-Mushrikûn will abide in the Fire of Hell. They are the worst of creatures.
According to the above Ayah, the people of the Scripture are
the Jews and
the Christians. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.