Of Prayer, by John Calvin, tr. Henry Beveridge , at sacred-texts.com
Sometimes, however, the saints in supplicating God, seem to appeal to their own righteousness, as when David says, "Preserve my soul; for I am holy" (Psalm 86:2). Also Hezekiah, "Remember now, O Lord, I beseech thee how I have walked before thee in truth, and with a perfect heart, and have done that which is good in thy sight" (Isaiah 38:2). All they mean by such expressions is, that regeneration declares them to be among the servants and children to whom God engages that he will show favour. We have already seen how he declares by the Psalmist that his eyes "are upon the righteous, and his ears are open unto their cry" (Psalm 34:16Ps. 34:16) and again by the apostle, that "whatsoever we ask of him we obtain, because we keep his commandments" (John 3:22). In these passages he does not fix a value on prayer as a meritorious work, but designs to establish the confidence of those who are conscious of an unfeigned integrity and innocence, such as all believers should possess. For the saying of the blind man who had received his sight is in perfect accordance with divine truth, And God heareth not sinners (John 9:31); provided we take the term sinners in the sense commonly used by Scripture to mean those who, without any desire for righteousness, are sleeping secure in their sins; since no heart will ever rise to genuine prayer that does not at the same time long for holiness. Those supplications in which the saints allude to their purity and integrity correspond to such promises, that they may thus have, in their own experience, a manifestation of that which all the servants of God are made to expect. Thus they almost always use this mode of prayer when before God they compare themselves with their enemies, from whose injustice they long to be delivered by his hand. When making such comparisons, there is no wonder that they bring forward their integrity and simplicity of heart, that thus, by the justice of their cause, the Lord may be the more disposed to give them succour. We rob not the pious breast of the privilege of enjoying a consciousness of purity before the Lord, and thus feeling assured of the promises with which he comforts and supports his true worshippers, but we would have them to lay aside all thought of their own merits and found their confidence of success in prayer solely on the divine mercy.