2 He who walks uprightly, And works righteousness, And speaks the truth in his heart;
New Living Translation
2 Those who lead blameless lives and do what is right, speaking the truth from sincere hearts.
Matthew Henry's Commentary on Psalm 15:2
The way to heaven, if we would be happy, we must be holy. We are encouraged to walk in that way.
Here is a very serious question concerning the character of a citizen of Zion. It is the happiness of glorified saints, that they dwell in the holy hill; they are at home there, they shall be for ever there. It concerns us to make it sure to ourselves that we have a place among them. A very plain and particular answer is here given. Those who desire to know their duty, will find the Scripture a very faithful director, and conscience a faithful monitor. A citizen of Zion is sincere in his religion. He is really what he professes to be, and endeavours to stand complete in all the will of God. He is just both to God and man; and, in speaking to both, speaks the truth in his heart. He scorns and abhors wrong and fraud; he cannot reckon that a good bargain, nor a saving one, which is made with a lie; and knows that he who wrongs his neighbour will prove, in the end, to have most injured himself. He is very careful to do hurt to no man. He speaks evil of no man, makes not others' faults the matter of his common talk; he makes the best of every body, and the worst of nobody. If an ill-natured story be told him, he will disprove it if he can; if not, it goes no further. He values men by their virtue and piety. Wicked people are vile people, worthless, and good for nothing; so the word signifies. He thinks the worse of no man's piety for his poverty and mean condition. He reckons that serious piety puts honour upon a man, more than wealth, or a great name. He honours such, desires their conversation and an interest in their prayers, is glad to show them respect, or do them a kindness. By this we may judge of ourselves in some measure. Even wise and good men may swear to their own hurt: but see how strong the obligation is, a man must rather suffer loss to himself and his family, than wrong his neighbour. He will not increase his estate by extortion, or by bribery. He will not, for any gain, or hope of it to himself, do any thing to hurt a righteous cause. Every true living member of the church, like the church itself, is built upon a Rock. He that doeth these things shall not be moved for ever. The grace of God shall always be sufficient for him. The union of these tempers and this conduct, can only spring from repentance for sin, faith in the Saviour, and love to him. In these respects let us examine and prove our own selves.
Those that forsake the ways of the Lord, depart from their God. But though conscious to ourselves of many a false step, let there not be a wicked departure from our God. David kept his eye upon the rule of God's commands. Constant care to keep from that sin, whatever it be, which most easily besets us, proves that we are upright before God. Those who show mercy to others, even they need mercy. Those who are faithful to God, shall find him all that to them which he has promised to be. The words of the Lord are pure words, very sure to be depended on, and very sweet to be delighted in. Those who resist God, and walk contrary to him, shall find that he will walk contrary to them, Leviticus 26:21-24. The gracious recompence of which David spoke, may generally be expected by those who act from right motives. Hence he speaks comfort to the humble, and terror to the proud; "Thou wilt bring down high looks." And he speaks encouragement to himself; "Thou wilt light my candle:" thou wilt revive and comfort my sorrowful spirit; thou wilt guide my way, that I may avoid the snares laid for me. Thou wilt light my candle to work by, and give me an opportunity of serving thee. Let those that walk in darkness, and labour under discouragements, take courage; God himself will be a Light to them.