Albert Barnes Commentary Psalms 78:68

"But chose the tribe of Judah, The mount Zion which he loved." — Psalms 78:68 (ASV)

But chose the tribe of Judah - He chose David of the tribe of Judah as ruler and king; he chose a place within the limits of Judah, namely, Mount Zion, or Jerusalem, as the place where his worship was to be celebrated. Thus, the ancient prediction regarding the supremacy of Judah was accomplished (Genesis 49:8–10).

The Mount Zion, which he loved - Which he chose, for which he had an affection .