Psalm 15 - Lord who shall sojourn in Your tabernacle?
Longing for the practical living out of the righteousness of Christ, because it qualifies us to dwell in God's house in this age and in eternity in the mountain of His holiness, which is the New Jerusalem.
None of the qualifying righteousnesses listed here are religious or spiritual things: not Old Testament things like keeping the Sabbath, nor even things like meditating on the Lord's word, or spending time in His presence.
Keeping the religious and spiritual things in the Bible should result in the living in this psalm. The simple righteousnesses in this Psalm seem common. They are things a person who has never read the Bible knows already. But living them out is not common. The test of true religion is such a life that manifests itself to every man's conscience.
v4 The humble person looks upon every child of God, the most weak and unworthy, and honors him and prefers him as a son of the King. - Andrew Murray
ref. Prov 17:15 He that justifieth the wicked, and he that condemns the righteous, even they both are abomination to Jehovah.
The 2 questions in the beginning of the Psalm are only partially answered here in this Psalm. As in our prayers, a further answer will come in the Psalms to follow.