What is valid depends on many things.
I think it’s pretty clear that if you accpet any validity from the early Jewish texts of the Old Testament, they are confirmed and made valid by the New Testament.
As much as I think Islam is a false religion, it confirms or validates much of the Jewish and Christian texts. Since it perverts both in fundamental doctrine I reject Muhammed as a prophet of God, but think of him as more as a Joseph Smith type character who uses the truth for their own gains, not for Gods glory.
Even with the Islamic, Mormon, JW and other perversions to Christianity, the fact that over half the worlds population recognize Christ as a valid figure with respect to God is nothing to dismiss lightly. Excluding those faiths, over 1/3 of humans acknowledge Christ as what He said He was.
The nearest in size to the Christian faith is Islam at 1/6 the world population. Almost equal in size to Islam is grouped Agnostic/Atheist/Non-religious.
What else would validate it to your satisfaction?