Hebrews 3-4 (among many others; John 14:15; Exodus 20:6; Isaiah 56:1,8; John 10:16; Isaiah 56:2-7, Acts 4:24, 14:15; Revelation 10:6, 14:6-7, &c).
Hebrews 3-4 is clear.
Hebrews 4:3, "my (God's) rest" and "the works were finished from the foundation of the world", which is a direct reference to...