“I lift my eyes to the hills. From where does my help come from? My help comes from the Lord, who made heaven and earth. He will not let your foot be moved; he who keeps you will not slumber. Behold, he who keeps Israel will neither slumber nor sleep” Psalm 121:1-4
This is a song of ascents, which were songs of praise that God’s people would sing on their way to Jerusalem to celebrate the various festivals. In this Psalm, David recounts several times that his help comes from the Lord. In fact, he uses the word keep or some variation of the word keep six times. Thus, the melodic line or theme of this psalm is that God keeps those who are his. Further, “Anthony Cresko points out that the word samar in v. 5a occurs in the middle of the psalm – an equal number of syllables come before and after the word – and therefore suggests that the Lord’s ‘guarding’ of the psalm-singer is the central message of the psalm.”
But what does the word keep or guard mean? The NICOT (New International Commentary on the Old Testament) had this to say concerning the word keep or guard:
The verbal root samar means ‘protect, guard, watch over, take care of…The word is rendered in a number of English translations as ‘keep’ (RSV, NRSV, NASB), but the word conveys a more active concept. The Lord does not just ‘keep’ the psalmist in the sense of providing a space for the psalmist. But the Lord ‘guards, protects, watches over’ the psalmist, fending off those who seek out the psalmist or who would do the psalmist harm.
Later in the New Testament, we see in the book of Romans Paul shares a similar word when he writes, “Who shall separate us from the love of Christ? Shall tribulation, or distress, or persecution, or famine, or nakedness, or danger, or sword? As it is written, ‘For your sake we are being killed all the day long; we are regarded as sheep to be slaughtered.’ No, in all these things we are more than conquerors through him who loved us. For I am sure that neither death nor life, nor angels nor rulers, nor things present nor things to come, nor powers, nor height nor depth, nor anything else in all creation, will be able to separate us from the love of God in Christ Jesus our Lord.”
In a word, God keeps us; he guards us in his Son Jesus, despite anything that comes into the life of a believer. Thus the question, “where does your help come from” is answered with one word: Jesus.
 “Psalm 121: Prayer of a Warrior?” Bib 70 (1989) 499.
 deClaisse-Walford, Nancy, Rolf. A. Jacobson, Beth LaNeel Tanner. The Book of Psalms, William B. Eerdmans, 2014, pp. 896-897. The New International Commentary on the Old Testament.