Albert Barnes Commentary Psalms 65:8

"They also that dwell in the uttermost parts are afraid at thy tokens: Thou makest the outgoings of the morning and evening to rejoice." — Psalms 65:8 (ASV)

They also who dwell in the remotest parts - That is, those who dwell in the remotest regions, far from civilized lands, far from those places where people are instructed about the causes of the events that occur, and about the being and character of the great God who performs these wonders.

The idea is that even they see enough evidence of the divine presence and power to fill their minds with awe. In other words, in all lands, there is evidence of the divine existence and might. There is enough to fill people's minds with awe and make them solemn.

Are afraid - Thus the thunder, the storm, the tempest, the earthquake, or the eclipse of the sun or moon fill the minds of peoples in remote regions with terror.

At your tokens - Or signs. That is, the signs that really indicate the existence, the presence, and the power of God.

You make the outgoings - The word rendered "outgoings" properly means a going forth, as of the rising of the sun (Psalms 19:7); and then, a place of going forth, or from which anything goes forth, such as a gate or door (Ezekiel 42:11), or fountains from which water issues (Isaiah 41:18). Hence, it refers to the east, where the sun seems to come forth from its hiding-place.

The representation here is that the morning seems to come forth, or that the rays of light stream out from the east; and, in like manner, the fading light of the evening—the twilight—seems to come from the west.

Of the morning and evening to rejoice - The allusion is to the east and the west. The sun in its rising and setting seems to rejoice; that is, it appears happy, bright, cheerful. The margin reads "to sing"—a poetic expression indicating exultation and joy.