Psalm 121 is one of fifteen "Songs of Ascents" (120-134), psalms the Israelites sang as they went up to worship at the temple in Jerusalem. Its main theme–that the LORD is the unfailing Protector of those who look to him–surely made it appropriate for such use. However, it is equally appropriate for God's pilgrims on the journey of life. We confess that our security comes from the LORD, the Maker and Ruler of all creation, and receive assurance that the LORD never sleeps (st. 1), but watches over us day and night to protect us from harm no matter where we go (st. 2). The (altered) versification is from the 1912 Psalter. Other settings of Psalm 121 are at 180 and 448.
Psalter Hymnal Handbook
This song includes a plea and a prayer seeking God’s leading and care. Those who seek this leading can know that the Holy Spirit always aims to provide just such care for the believer. He not only renews our hearts, but also “leads us into truth, and helps us to pray, stands by us in our need, and makes our obedience fresh and vibrant” (Our World Belongs to God, paragraph 29).