The last clause of verse 5 could be translated, “We heard a voice we had not known” (niv margin), referring to the message God sent in verses 6–10. At some point in the festal celebration, a priest received God’s message and declared it to the people. The emphasis in this psalm is on hearing the Word of God (vv. 6, 11, 13; see 95:7–11; Heb. 3). Every seventh year at the Feast of Tabernacles, the priests read the book of Deuteronomy to the people, and perhaps this was one of those special sabbatical years. (See Deut. 31:9–13, and note the emphasis in Deuteronomy on “hearing God” [Deut. 4:1, 6, 10; 5:1; 6:3–4; 9:1].) It is delightful to sing praises to God and to pray, but if we want Him to listen to us, we must listen to Him.
Frequently the Lord reminded His people of their miraculous deliverance from Egypt (v. 6), the power of God that accomplished it, and the love of God that motivated it. He also reminded them of the covenant they accepted at Sinai (v. 7a; see Deut. 5:2–3). The people hearing this message were not at Sinai, but the decision of their ancestors was binding on them and their descendants. God’s message also mentioned their failure to trust Him at Meribah (Ex. 17; Num. 20). At the Feast of Tabernacles, the priests poured out water in the temple to commemorate these events (John 7:37–39). The Lord emphasized that He would not tolerate His people worshipping idols (vv. 8–9; Ex. 20:1–4; Deut. 4:15–20). What could the false gods of the neighboring nations give to them? “Open your mouth wide and I will fill it” (v. 10 nasb).