'Observe' in the Bible

and the statutes and the ordinances, and the law and the commandment, which he wrote for you, ye shall observe to do for evermore; and ye shall not fear other gods:

neither will I cause the feet of Israel to wander any more out of the land which I gave their fathers, if only they will observe to do according to all that I have commanded them, and according to all the law that my servant Moses commanded them.