When the Holy Qur’an was revealed, some people were followers of Judaism and some Christianity. Hence, the Islamic sacred law has established guidelines regarding interaction with the Jews and the Christians. So, do not ever, any one of you, add on to what is in Islam and what is in this religion. The Jews are the People of the Book, which is the Torah that the Prophet Musa u came with, while the Christians are also the People of the Book which is the Gospel that Prophet Isa u came with and that Allah U says:

﴾لَتَجِدَنَّ أَشَدَّ النّاسِ عَداوَةً لِلَّذينَ آمَنُوا اليَهودَ وَالَّذينَ أَشرَكوا﴿

“Surely You will find the most hostile of all people towards the believers to be the Jews and the polytheists” [Surah Al-Ma’idah: 82] and

﴾وَلَتَجِدَنَّ أَقرَبَهُم مَوَدَّةً لِلَّذينَ آمَنُوا الَّذينَ قالوا إِنّا نَصارىٰ﴿

“and surely you will find the nearest of them in affection to the believers to be those who say ‘We are Christians.’” [Surah Al-Ma’idah: 82].