John Gill Commentary Psalms 122:4

"Whither the tribes go up, even the tribes of Jehovah, [For] an ordinance for Israel, To give thanks unto the name of Jehovah." — Psalms 122:4 (ASV)

Whither the tribes go up, the tribes of the Lord
The twelve tribes of Israel; the males of them went up three times a year to Jerusalem to worship, at the feasts of passover, pentecost, and tabernacles; and was typical of the church of Christ, where the worship of God is carried on, his word preached, and ordinances administered; and whither saints go and attend for their own profit and the glory of God; this is the city of our solemnities, (Isaiah 33:20) (56:7) ;

unto the testimony of Israel ;
the ark of the testimony a symbol of the divine Presence. The law is called a testimony, because it testified the will of God to be done; this was put into an ark, which had its name from thence, and was typical of Christ, the end of the law for righteousness; and over the ark was the divine Presence: hither the tribes came to worship God, and to consult him;``who (the Targum here says} testifies to Israel, that his divine Majesty dwells among them, when they go to confess unto the name of the Lord.''

The Gospel is called the testimony of Christ; and it is what testifies concerning his person, office, and grace, unto the Israel of God; and who go up to the house of God in order to hear it;

to give thanks unto the name of the Lord;
for all his mercies and blessings, both temporal and spiritual; and which should be acknowledged, not only in a private manner, but publicly in the house of God; see (Psalms 100:4) (111:1) .