'Observe' in the Bible

Only, be strong and very courageous, to observe to do according to all the law which Moses My servant commanded thee; thou dost not turn aside from it right or left, so that thou dost act wisely in every place whither thou goest;

the book of this law doth not depart out of thy mouth, and thou hast meditated in it by day and by night, so that thou dost observe to do according to all that is written in it, for then thou dost cause thy way to prosper, and then thou dost act wisely.