Exodus 19:1

In the third month after they came out of Egypt. It is computed that the law was given just fifty days after their coming out of Egypt, in remembrance of which the feast of Pentecost was observed the fiftieth day after the passover, and in compliance with which the spirit was poured out upon the apostles, at the feast of Pentecost, fifty days after the death of Christ. Mount Sinai was a place which nature, not art, had made conspicuous, for it was the highest in all that range of mountains. Thus God put contempt upon cities and palaces, setting up his pavilion on the top of a mountain, in a barren desert. It is called Sinai, from the multitude of thorny bushes that over — spread it.