John Gill Commentary Psalms 122:9

"For the sake of the house of Jehovah our God I will seek thy good." — Psalms 122:9 (ASV)

Because of the house of the Lord our God
Not because of his own palace, nor because of his own house and family; nor because of his own personal interest; though all were concerned in the peace of Jerusalem: but chiefly because of the sanctuary of the Lord, as the Targum; because of the worship and service of God in it; because of his great love and zeal for the house and church of the living God, which ate him up, (Psalms 69:9) ;

I will seek your good ;
the good of Jerusalem, the good of the church of God; do all the good he could to it both with his purse and prayers, and by stirring up others to do the same; see (Psalms 51:18) .