Hebrews 12:1 says,
"Therefore, since we are surrounded by such a great cloud of witnesses, let us throw off everything that hinders and the sin that so easily entangles."
Hebrews 11 contains a list of Jewish people from the Old Testament who lived by faith.
They are the great cloud of witnesses that “we” (the Jewish-Hebrew people) were surrounded by, serving as an example to them of those who lived by faith.
The reason Hebrews 11 exists, the chapter on faith, was to prove to the Jewish people that living by faith was not a foreign way of life for Jewish people.