This is one of the songs of ascents, perhaps sung as the pilgrims journeyed to the temple for festival worship. Several images suggest travel: the hills, where danger may lurk (v. 1); the fierce heat of the Palestinian sun (v. 6); the many uncertainties of the night (v. 6); the "going out and coming in" (v. 8)--though this can also refer to any human undertaking (Deuteronomy 28:6). The reference to being "moonstruck" (v. 6) may reflect the notion that the moon (or moon god) can have negative effects on people, but that is not certain.
Certain is that, in all things, God "keeps Israel" (vv. 4, 5, 7, 8), a very important word in the psalm. To "keep" is also to "watch over" (same Hebrew word), which the psalm promises that God will do always and forever--not that believers are protected from all worldly harm, but that finally, with God, nothing can "strike" you. Though sometimes, given present difficulties, it may seem to the pray-er that God is asleep (Psalm 44:23), this psalm reassures the hearer that this is never actually true. The Lord is always on watch.
Another strong, yet gentle, image is God as "shade" (v. 5). Shade is nothing (it can't be bottled or weighed), yet it is everything, especially when the sun is hot. God, too, is Israel's invisible keeper, whose presence is a matter of life and death.
1 I lift up my eyes to the hills
from where will my help come?
2 My help comes from the Lord,
who made heaven and earth.
3 He will not let your foot be moved;
he who keeps you will not slumber.
4 He who keeps Israel
will neither slumber nor sleep.
5 The Lord is your keeper;
the Lord is your shade at your right hand.
6 The sun shall not strike you by day,
nor the moon by night.
7 The Lord will keep you from all evil;
he will keep your life.
8 The Lord will keep
your going out and your coming in
from this time on and for evermore.
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org