Traditional Christian doctrines
Unfortunately, some of the most basic things believed by most professing Christians derive from ancient paganism rather than from the Bible. The idea that people have immortal souls was first taught in ancient Egypt and Babylon. The Greeks likewise taught that at death the soul would separate from the physical body ( Jewish Encyclopedia , 1941, Vol. 6, pp. 564, 566, "Immortality of the Soul"). That idea was merged into Christianity from Greek philosophy. It did not come from inspired Scripture.
The ancient Egyptians developed the concept of going to heaven. In their mythology, the god Osiris was killed but then raised back to life, whereupon he went to a distant heavenly realm. The Egyptians concluded that if he could do this, then human beings could follow ( Lewis Browne, This Believing World , pp. 83-84). This heavenly reward was a central teaching of several ancient mystery religions—but not the religion of the Hebrews or early Christians.
Even some Christian teachings about Jesus have origins in paganism rather than the Biblical record. Babylonian mythology regarding Ishtar claimed that she had a son named Tammuz. He died each year, but then would be reborn again in the spring. The Babylonian veneration of both the mother and child influenced later versions of Christianity that deified Jesus' mother Mary as much as Jesus Himself (Sir James Frazer, The Golden Bough , 1993, p. 326). This stands in contrast to Scripture, which honors Mary, but reveres no ordinary human being—only Christ.
The Chaldean symbol for Tammuz was the letter tau , which appears as a san-serif "t" and is commonly considered a cross ( Babylonian Mystery Religion , p. 51; Vine's, "Cross, Crucify"). While the Bible does indeed teach that Jesus was crucified, there is no record of the shape of the crucifix. At that time, Romans used various forms of upright stakes, some with crossbeams and some without. The Bible gives no indication that the early Church ever used the cross as a religious symbol, but several pagan religions had been doing so for centuries before Christ was born.
This sounds similar to Rev. Alexander Hislop's book:
The Two Babylons, or The Papal Worship Proved to be the Worship of Nimrod and His Wife
What it shows is the universal desire for everlasting life after our time in this world. Fortunately, we have found the true path, the WAY, in our Lord and Saviour, Jesus Christ.