The last part of the psalm runs over with joyful vows--first, of magnifying God's name (vv. 13-15), and then of offering true sacrifices. A man who has passed through such experiences as the psalmist's, and has received the blessings for which he prayed, cannot be silent. The instinct of hearts touched by God's mercies is to speak of them to others. And no man who can say "I will tell what He has done for my soul" is without the most persuasive argument to bring to bear on others. A piece of autobiography will touch men who are unaffected by elaborate reasonings and deaf to polished eloquence. The impulse and the capacity to "teach transgressors Thy ways" are given in the experience of sin and forgiveness; and if any one has not the former, it is questionable whether he has, in any real sense or large measure, received the latter. The prayer for deliverance from blood-guiltiness in ver. 14 breaks for a moment the flow of vows; but only for a moment. It indicates how amid them the psalmist preserved his sense of guilt, and how little he was disposed to think lightly of the sins of whose forgiveness he had prayed himself into the assurance. Its emergence here, like a black rock pushing its grimness up through a sparkling, sunny sea, is no sign of doubt whether his prayers had been answered; but it marks the abiding sense of sinfulness, which must ever accompany abiding gratitude for pardon and abiding holiness of heart. It seems hard to believe, as the advocates of a national reference in the psalm are obliged to do, that "blood-guiltiness" has no special reference to the psalmist's crime, but is employed simply as typical of sin in general. The mention of it finds a very obvious explanation on the hypothesis of Davidic authorship, and a rather constrained one on any other. Ver. 16 introduces the reason for the preceding vow of grateful praise, as is shown by the initial "For." The psalmist will bring the sacrifices of a grateful heart making his lips musical, because he has learned that these, and not ritual offerings, are acceptable. The same depreciation of external sacrifices is strongly expressed in Psalm xl. 6, and here, as there, is not to be taken as an absolute condemnation of these, but as setting them decisively below spiritual service. To suppose that prophets or psalmists waged a polemic against ritual observances _per se_ misapprehends their position entirely. They do war against "the sacrifice of the wicked," against external acts which had no inward reality corresponding to them, against reliance on the outward and its undue exaltation. The authors of the later addition to this psalm had a true conception of its drift when they appended to it, not as a correction of a heretical tendency, but as a liturgical addition in full harmony with its spirit, the vow to "offer whole burnt offerings on" the restored "altar," when God should again build up Zion.