As it is written there is none righteous - The apostle reasoning with Jews; shows from their own Scriptures that the Jews, in the matter of justification, had no advantage over the Gentiles; that the Jew had failed to keep the written Law given him, as the Gentile; and that both were equally dependent on the mercy of God, incapable of being justified and saved by their works. Indeed there is none righteous, no, not one, but those who are justified by the righteousness of Christ imputed to them. The quotation in Romans 3:10-12, is from Psalm 14:1-7, or Psalm 53:1-6 with some variation. Barnes Notes on the Bible

There is none that understand; This is rightly concluded, from what the Psalmist says, Psalm 14:2, 'The Lord looked down from heaven upon the children of men', on all the children of men, Jews and Gentiles, 'to see if there were any that did understand'; and it appears, upon this survey of them, there was not one understanding person among them: man thinks himself a very wise and understanding creature, though he is born a very ignorant one.

There is none that seek after God; who prays with understanding; who seek him with their whole hearts, in Christ, and under the Spirit. Psalms 14:2

They are all gone out of the way; In Psalm 14:3; it is said, 'they are all gone aside'; as persons in debt: all have contracted large and numerous debts. Christ has paid the debt of his people. In Psalm 53:3, it is rendered, 'everyone of them is gone back'; that is, from God; from his commands, and from their former state and condition: here the phrase is rendered by the apostle, 'they are all gone out of the way': that is, out of the way of God and his precepts, out of the way of holiness and righteousness, of light and life; into their own ways.

They are together become unprofitable; the word in Psalm 14:3 and Psalm 53:3; is translated, 'they are become filthy'. This word in Hebrew means to become 'putrid and offensive,' like fruit that is spoiled. In Arabic, it is applied to milk that becomes sour. Applied to moral subjects, it means to become corrupt and useless. They are of no value in regard to works of righteousness. Barnes Notes on the Bible

There is none that does good, no, not one; again from Psalm 14:1; and therefore must be unprofitable. There is none that can do good perfectly, apart from the grace of God, Christ, and of the Spirit; and there is not even a spiritual man.

Their throat is an open sepulchre; The throat is said to be an open sepulchre, as in Psalm 5:9, both as an instrument of speech and as an instrument of swallowing, and so may denote the sinner's greediness for sin, in pleasure and abundance. Corrupt communication persons fall unawares to are dangerous and hurtful.

With their tongues they have used deceit; The sin of flattery, for the words in Psalm 5:9; 'they flatter with their tongue'; either God or men, themselves or others for there are flatterers in things sacred and civil.

The poison of asps is under their lips or as in Psalm 140:3, 'adders poison is under their lips'. The asp is but a small creature, and so is the tongue, James 3:5, but there is a world of mischief in it, signified by poison; which, as that, is latent and secret, is under it; and as that stupefies and kills insensibly, so an evil tongue in a deadly and incurable manner: oftentimes the Jews speak of the evil imagination, or corruption of nature entering into persons, and operating in them, 'as poison in an angry serpent'.

Whose mouth is full of cursing and bitterness These words are taken from Psalm 10:7, by cursing is meant, cursing of God, with the heart and mouth. Cursing of parents and fellow creatures: 'whose mouth full', denotes the frequency of the sin; scarce anything else comes out of it but cursing; which discovers the sad corruption of the heart; 'for out of the abundance of the heart the mouth speaks', Matthew 12:34. By 'bitterness' is meant, either sin in general or sinful words, such as oaths, curses, and deceitful words.

Their feet are swift to shed blood The sins of the heart and mouth are before described, and now the sins of action are taken notice of; for 'the feet' denotes the readiness and eagerness of men towards malice and hatred. The words are cited from Isaiah 59:7, and seem to point at the times of Manasseh, who shed so much innocent blood, as to fill Jerusalem with it from one end to the other.

Destruction and misery are in their ways This passage also is to be found in Isaiah 59:7, and they themselves are brought to misery: the way they are walking in is, 'the broad way, that leads to destruction', Matthew 7:13; the end of it is eternal death, the destruction of the body and soul in hell, which will be attended with endless and inexpressible misery. Gill

And the way of peace have they not known This is a citation front Isaiah 59:8, and expresses the ignorance of mankind, with regard to true peace, and the way unto it: of Christ the peacemaker, and of the Gospel, which reveals and publishes it. They are ready to think it must be had by doing something of their own, and not that it is to be had only in Christ, in his blood and righteousness. They are ignorant of the paths of wisdom, which are peace; they imagine something done by the creature is the way; and are ignorant that Christ is the only way of salvation, they do not study peace, but rather contention.

There is no fear of God before their eyes The place referred to is Psalm 36:1, by the 'fear of God', is meant a reverential affection for God, consistent with faith, opposed to pride and haughtiness, and is a blessing of the covenant of grace. Gill's Exposition of the Entire Bible