Serve the Lord with fear - With reverence, and with deep apprehensions of the consequences of not serving and obeying him. That is, serve him in not opposing, but in promoting his purpose of establishing a kingdom under the Messiah, with the deep apprehension that if you do not do it, he will arise and crush you in his wrath.
And rejoice - Prof. Alexander renders this “shout,” and supposes that it refers to the customary recognition of a present sovereign. The word used - גיל gı̂yl - means properly to move in a circle, to revolve; and then to dance in a circle, to exult, to rejoice. Then, according to Gesenius, it means to tremble, to fear, from the leaping or palpitation of the heart Job 37:1; Hosea 10:5; Psalms 29:6. Gesenius renders it here “fear with trembling.” The common translation, however, better expresses the sense. It means that they should welcome the purposes of Yahweh, and exult in his reign, but that it should be done with a suitable apprehension of his majesty and power, and with the reverence which becomes the public acknowledgment of God.
With trembling - With reverence and awe, feeling that he has almighty power, and that the consequences of being found opposed to him must be overwhelming and awful. The duty here enjoined on kings and rulers is that of welcoming the purposes of God, and of bringing their influence - derived from the station which they occupy - to bear in promoting the reign of truth upon the earth - a duty binding on kings and princes as well as on other men. The feelings with which this is to be done are those which belong to transactions in which the honor and the reign of God are concerned. They are mingled feelings, derived from the mercy of God on the one hand, and from his wrath on the other; from the hope which his promise and purpose inspires, and from the apprehension derived from his warnings and threatenings.