This article examines the background of the concept of Sabbath rest (σαββατισμός) in Heb 4.1–11. Special attention is given to the relation between God's rest and God's activity, which seemingly are in tension with each other: on the one hand, the author's argument is based on the assumption that God entered his rest at the seventh day of creation and stopped working forever (4.10); on the other hand, there is a clear reference to God's works after creation (3.9–10). A comparison with Philo's explanations of the seventh day of creation, however, reveals that for a Jewish Middle Platonist this tension does not appear to be a problem because rest and activity in God are two sides of the same coin. It is argued that this background helps to explain Hebrews’ concept of Sabbath rest. A concluding outlook shows that the suggested Middle Platonic understanding of Hebrews 4 fits well the context of the epistle as a whole, as the same coexistence of rest and activity can also be found in Hebrews 7 in relation to Jesus’ intercession in the heavenly tabernacle.