Heb. 12:1, "A great cloud of witnesses."

"Therefore, since we have so great a cloud of witnesses surrounding us, let us also lay aside every encumbrance, and the sin which so easily entangles us, and let us run with endurance the race that is set before us," (Heb. 12:1).

The great crowd of witnesses surrounding us is the list of godly people mentioned in the previous chapter:  Noah, Abraham, Isaac, Jacob, Joseph, Moses, Gideon, Barak, Samson, Jephthah, of David and Samuel and the prophets.  They are those who looked to God and truth and, though they were not perfect, trusted in peak hope of the coming Messiah.

Or are different interpretations offered by various religious groups. Catholics tend to see the cloud of witnesses as the same of old to whom they are able to pray. Of course, Catholics do not generally admit they pray to saints. Instead, they say they pray with them to God. Whatever their position, prayer to the dead is never taught in Scripture.

The Jehovah's Witnesses interpret the great cloud of witnesses to be "pre Jehovah's Witnesses."  The Mormons say that includes their founder Joseph Smith and other prominent Mormons."