The problem of determining the date of the individual psalms and of the different collections is exceedingly difficult, both because the superscriptions were clearly added by later editors who thought thereby to connect the psalm with an earlier writer or historic incident, and because the psalms themselves contain few historical allusions. A great majority of them reflect the teachings of the pre-exilic prophets or, like the book of Proverbs, come from the lips of the sages and deal with universal human problems. Some were written by priests or Levites for use in connection with the song service of the temple. Because of this timeless quality, however, an appreciation of them does not depend upon an exact knowledge of their authorship or historical background. It is possible that a few of the psalms in the first part of the Psalter come from the pre-exilic period, but the great majority reflect the problems, the hopes, the fears, and the trials of the faithful who lived under the shadow of the second temple. While the superscriptions clearly do not come from the original psalmists themselves, they do record the conclusions of the editors who made the earliest collections. The oft-recurring title "Psalm to David" either means that by the editor it was attributed to David as the author, or is a general designation of psalms that were recognized to be comparatively early. The two great Davidic collections, 3-41 and 51-72, were apparently collected not long after the rebuilding of the walls of Jerusalem. They are deeply influenced by the inspiring teachings of the II Isaiah. They are remarkably free from that ceremonialism which became a powerful force in Judaism during the last century of the Persian rule. Psalm 51:16, 17, for example, echoes the noble ethical teachings of the great prophets: Thou desirest not sacrifice, else would I give it, Thou delightest not in burnt offering, The sacrifice of God is a broken heart, A broken and a contrite heart, O God, thou wilt not despise. They represent, therefore, the oldest edition of the Psalter and the songs which were probably sung by the temple singers and the people as they went up to the temple on the great feast days during the closing years of the Persian period.