While most of the previous psalms have been serious pleas to God for help in times of utmost distress, Psalm 15 is asking just one question--who can get close to God?
The speaker is framing these question in terms of the landscape of Israel at the time, asking who can abide in God's tabernacle (this was in King David's time, before his son King Solomon built the first temple), and who can live on the holy hill where the tabernacle stays. In modern terms, the question could just be about who can belong to God and walk in fellowship with him.
Verses 2-3 describe the kind of person who can get close to God: someone who performs righteousness. He is not self-deceived, he doesn't cut others down with his words, and doesn't seek to harm or blame others. Sounds pretty simple, until I consider how often I feel bitterness in my heart or try to make someone feel less-than-worthy with the words I direct toward them. Maybe abiding with God takes more work than I think.
Verses 4-5 give further details about this godly person. She does not approve of vile people (note that there is a big difference between not speaking evil about another person and approving of everything they do--hate the sin, not the sinner, as they say). She honors those who honor and respect God (other believers), she does not go back on her promises, even when it is difficult to stick by them. She doesn't loan money at high interest rates (this is comparable to cheating others in any way, not just money-lending).
The person, man or woman, who does these things is secure in the Lord and will never be moved.
1Lord, who shall abide in thy tabernacle? who shall dwell in thy holy hill?
2 He that walketh uprightly, and worketh righteousness, and speaketh the truth in his heart.
3 He that backbiteth not with his tongue, nor doeth evil to his neighbour, nor taketh up a reproach against his neighbour.
4 In whose eyes a vile person is contemned; but he honoureth them that fear the Lord. He that sweareth to his own hurt, and changeth not.
5 He that putteth not out his money to usury, nor taketh reward against the innocent. He that doeth these things shall never be moved.