What are the similarities and differences between Islam, Christianity and Judaism?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam,  is His slave and Messenger.

Islam is the submission and surrender to Allaah The Almighty and believing in the Oneness of His Lordship, Divinity and Names and Attributes. It also means submitting to Allaah The Almighty by fulfilling His commands and avoiding His prohibitions. In this sense, Islam is the religion of all prophets.

Hence, the previous Prophets advised their followers to adhere to Islam. Ibraaheem (Abraham) and Ya‘qoob (Jacob), may Allaah exalt their mention, say in the Quran, as Allaah The Almighty Says (what means): {And Ibraaheem instructed his sons [to do the same] and [so did] Ya‘qoob, [saying], "O my sons, indeed Allaah Has Chosen for you this religion, so do not die except while you are Muslims.”} [Quran 2:132]

Prophets did not differ in the basics and fundamentals of religion. Allaah The Almighty Says (what means): {He has ordained for you of religion what He enjoined upon Nooh (Noah) and that which We have revealed to you, [O Muhammad], and what We enjoined upon Ibraaheem and Moosa (Moses) and ‘Eesa (Jesus) - to establish the religion and not be divided therein. Difficult for those who associate others with Allaah is that to which you invite them. Allaah chooses for Himself whom He wills and guides to Himself whoever turns back [to Him].} [Quran 42:13]

The Prophet, sallallaahu ‘alayhi wa sallam, said: “The prophets are paternal brothers; their mothers are different, but their religion is one.” [Ahmad and others] [Al-Albaani: Saheeh]

The difference among Prophets is in terms of branches and legislations due to the different peoples, environments, times, places, etc of their mission. Whatever fits some people may not fit others. When humanity reached maturity by the successive Messages of Allaah and accumulation of historical and knowledgeable experiences, Allaah The Almighty sealed the Messages and approved what fits the whole humanity. He abrogated what does not fit humanity and left a broad space for Ijtihaad, i.e., reasoning in the light of revelation and general rules of the Sharee‘ah (Islamic law). Therefore, the Message of Muhammad, sallallaahu ‘alayhi wa sallam, is the last message for he is the last Prophet.

In this sense, Islam is not different from the religion which was brought by ‘Eesa, Moosa, or other Prophets, may Allaah exalt their mention. However, Islam differs from the distorted Christianity and Judaism especially in matters related to creed and Tawheed (Islamic Monotheism). The aspects of similarity between them are in matters of morals and good deeds which were originally revealed by Allaah The Almighty.

Allaah Knows best.