What does Christianity Judaisms and Islam have in common?

Answer 1

There isn't much, but here is a short list of commonalities:

1. Abraham is the common root for all three.
2. All three believe in One God i.e. All three are monotheistic faiths.
3. All three revere acts of kindness (Meccan suras, not later Medinan suras)
4. All three have a code of behavior

They are the three major Abrahamic religions. Abrahamic religions are monotheistic religions, i.e. only one god, that can all trace their belief systems back to an origin or spiritual connection to Abraham. Judaism was founded first, followed by Christianity in the first century, and Islam in the seventh century.

The father of all three religions was Abraham. Abraham's eldest son was the father of the religion of Islam, and Isaac, יצחק, was the father of Judaism, and Christianity broke of from Judaism when they thought Jesus was the Messiah.
Common with whom/what