Psalm 121 is a song of ascent, one of a collection of psalms (Psalms 120-134) with this title, likely used by pilgrims traveling to Jerusalem for worship. The author is unknown, and the occasion that prompted it is not specified. It is a lyrical poem that expresses trust in God's protection. The literary form is characterized by its use of affirmations and negations to emphasize God's role in safeguarding his people.
The psalm claims that God is the source of help and protection for his people, stating 'My help cometh from the LORD' and 'The LORD is thy keeper'. It argues that because God is the creator of heaven and earth, he is capable of preserving his people from harm. The psalm asserts that God is always vigilant, 'he that keepeth Israel shall neither slumber nor sleep', and that he will protect his people from all evil, preserving their 'going out and thy coming in'. The claim is that God's preservation is comprehensive and eternal, 'from this time forth, and even for evermore'.