Serve
`abad (aw-bad')
to work (in any sense); by implication, to serve, till, (causatively) enslave, etc.
the LORD
Yhovah (yeh-ho-vaw')
(the) self-Existent or Eternal; Jehovah, Jewish national name of God -- Jehovah, the Lord.
with fear
yir'ah (yir-aw')
fear (also used as infinitive); morally, reverence -- dreadful, exceedingly, fear(-fulness).
and rejoice
giyl (gheel)
to spin round (under the influence of any violent emotion), i.e. usually rejoice, or (as cringing) fear -- be glad, joy, be joyful, rejoice.
with trembling
ra`ad (rah'-ad)
a shudder -- trembling.