What does Psalm 118:7 mean?

It's possible this psalm was written after Israel returned from exile (Ezra 2:1) and had to contend with enemy nations while rebuilding Jerusalem (Nehemiah 4:7–9). Confidence in the Lord requires an understanding that nothing can stop His will—so nothing can happen to us which is not part of His good plan (Romans 8:28). The prior verse (Psalm 118:6) was cited in the book of Hebrews to make this very point (Hebrews 13:6).

A person can only say, "God is on my side" when they have a saving relationship with Him (Proverbs 1:7; 2 Corinthians 7:10; John 3:16). For those with saving faith, the Holy Spirit acts as a helper. This is something Jesus promised shortly before His crucifixion (John 14:16–18). There, Jesus uses the Greek word paraklētos, which suggests the defense lawyer who stands up for someone in a court of law. Here, the psalmist uses a phrase which most literally means "Yahweh is for me of the ones who support me." This seems to mean that God, out of all the psalmist's sources of aid, is the most powerful and important.