Which religions were similar to Muhammad's?

Answer 1

You should turn your question around, since the religions similar to Islam came before it.

Ask:

Muhammad's religion was similar to which others?

answer - Judaism, and its daughter-religion, Christianity.

There is no question that Islam, like Christianity, was heavily influenced by Judaism, directly and indirectly. Very many concepts and quotes in the Qur'an (the book of Islam) are taken verbatim from the Torah, the Hebrew prophets, and later Jewish teachings. The Talmud was already recorded in writing by no later than 500 CE*, before the time of Muhammad, making it a simple matter to quote from it too.*(Footnote: as stated in the Encyclopedia Brittanica, under "Talmud and Midrash.")

Examples:

1) Qur'an:

"...Whoever killed a human being, except as punishment for murder or other villainy, shall be deemed as though he had killed all mankind; and whoever saved a human life shall be deemed as though he had saved all mankind."

Judaism:

"Whoever kills a single individual it is considered that he has slain the entire world, but he who preserves the life of a single individual it is counted as if he has preserved the whole world." Mishnah Sanhedrin 4:5.

2) Qur'an:

The famous narrative of how the young Abraham smashed his father's idols -

Judaism:

- is taken from the Jewish midrash (Genesis Rabbah 38:11-13).

3) The following Hebrew-Bible characters are found in parallel Qur'an-narratives:

Adam, Enoch, Noah, Abraham, Lot, Ishmael, Isaac, Jacob, Joseph, Moses, Aaron, Jethro, David, Solomon, Elijah, Elisha, Jonah, Zachariah, and Job.

4) Arthur Jeffery writes in "The Foreign Vocabulary of the Quran", in page 1 of the introduction:

"One of the distinct impressions gleaned from a first perusal of the Quran, is that of the amount of material which is borrowed from the religions that were active in Arabia at the time when the Quran was in process of formation. It is plain that Muhammad drew his inspiration not from the religious life and experiences of his own land and his own people, but from the great monotheistic religions which were pressing down into Arabia in his day."

5) Charles Torrey in "The Jewish Foundation of Islam", writes on page 43:

"It was at home, not abroad, that the Muhammad received the Biblical and Haggadic narratives which occupy so large a part of the Koran."

Answer 2

Judaism and Christianity.