Matthew Henry Commentary Psalms 87:1-3

"His foundation is in the holy mountains. Jehovah loveth the gates of Zion More than all the dwellings of Jacob. Glorious things are spoken of thee, O city of God. Selah" — Psalms 87:1-3 (ASV)

Christ himself is the Foundation of the church, which God has laid. Holiness is the strength and firmness of the church.

Let us not be ashamed of the church of Christ in its humblest condition, nor of those that belong to it, since such glorious things are spoken of it. Other foundation can no man lay than that is laid, even Jesus Christ (1 Corinthians 3:11).

The glorious things spoken of Zion by the Spirit were all symbolic of Christ and his work and offices; of the gospel church, its privileges and members; and of heaven, its glory and perfect happiness.