'Service' in the Bible

About forty thousand armed for military service passed over before Jehovah to the war, unto the plains of Jericho.

But that it may be a witness between us, and you, and our generations after us, that we might do the service of the LORD before him with our burnt offerings, and with our sacrifices, and with our peace offerings; that your children may not say to our children in time to come, Ye have no part in the LORD.