O Lord, who may abide in your tent? Who may dwell on your holy hill?
Those who walk blamelessly, and do what is right, and speak the truth from their heart; who do not slander with their tongue, and do no evil to their friends, nor take up a reproach against their neighbors; in whose eyes the wicked are despised, but who honor those who fear the Lord; who stand by their oath even to their hurt; who do not lend money at interest, and do not take a bribe against the innocent. Those who do these things shall never be moved.
—Psalm 15
Where is God's holy hill? At the time this was written, it was Mount Zion in Jerusalem. There was the dwelling place of God on earth. In the Christian era, Zion refers not to a place, but to a people. For all the elect are collectively the body of Christ, and the body of Christ is the temple—God's earthly dwelling place.

So who may dwell in Zion, which is quite the same as asking in whom God may dwell (since Zion is now a people)? The standards mentioned are no less important today than they were then. First, walking blamelessly (or its parallel, doing what is right). What follows are not additions to the list, but the way the psalmist defines what it means to walk blamelessly/do what is right:
  • Tell the truth, not just outwardly but within—in other words don't just act right for appearances' sake, but have integrity.
  • Don't gossip.
  • Don't do hurtful things to friends or neighbors.
  • Despise the doings of wicked people.
  • Honor those who love God.
  • Keep one's word, no matter the cost.
  • Don't take advantage of the poor.
  • Don't pervert justice.
Sticking to these standards is like a rock to cling to in turbulent times. 

What's interesting here is that the standards set by so many Christians today don't include any of the things on this list. They're all about marriage and homosexuality and abortion and birth control and transgender people. One can stick to the standards of "evangelical" Christians and literally do none of the things listed in Psalm 15. So sometimes the old time religion is best, and those who claim to have a monopoly on it couldn't be further from it.

Help me to have high standards, O God, and thank you for showing me what those might look like. Thus may your word be my guide, and not the shouts of those around me. The shouts may be wrong; your word will not. Amen.