'Observe' in the Bible

'Observe for thyself that which I am commanding thee to-day: lo, I am casting out from before thee the Amorite, and the Canaanite, and the Hittite, and the Perizzite, and the Hivite, and the Jebusite;

'And a feast of weeks thou dost observe for thyself; first-fruits of wheat-harvest; and the feast of in-gathering, at the revolution of the year.