The LORD shall count, when he {f} writeth up the people, that this man was born there. Selah.

(f) When he calls them by his word into the Church, whom he had elected and written in the book.

Wesley's Notes

87:6 When - When God, the maker and governor of this city shall take a survey of all his citizens. It is an allusion to princes or governors of cities that use to write and keep a register of all their people.

Jamieson-Fausset-Brown Bible Commentary

6. The same idea is set forth under the figure of a register made by God (compare Isa 4:3).

Matthew Henry's Concise Commentary

87:4-7 The church of Christ is more glorious and excellent than the nations of the earth. In the records of heaven, the meanest of those who are born again stand registered. When God renders to every man according to his works, he shall observe who enjoyed the privileges of his sanctuary. To them much was given, and of them much will be required. Let those that dwell in Zion, mark this, and live up to their profession. Zion's songs shall be sung with joy and triumph. The springs of the joy of a carnal worldling are in wealth and pleasure; but of a gracious soul, in the word of God and prayer. All grace and consolation are derived from Christ, through his ordinances, to the souls of believers.