What are some biblical allusions from the book the alchemist

There are a few examples notable here:

The old man at the beginning of the book who sets the boy on his journey identifies himself only as "the king of Salem". Salem is an ancient name for Jerusalem. In the Book of Genesis from the Bible, the king of Salem is named Melchizedek and he is also identified as a priest from whom Abraham accepts a blessing and gives a tithe of 1/10 of all his possessions.

Jesus said, "If your leaders say to you, 'Look, the (Father's) kingdom is in the sky,' then the birds of the sky will precede you. If they say to you, 'It is in the sea,' then the fish will precede you. Rather, the (Father's) kingdom is within you and it is outside you. (emphasis added)

These are quoted directly from my source link below. Please take a look for even more detail.