Nahum M. Sarna, On the Book of Psalms, p. 139
A straightforward reading of this psalm conveys the picture of a pious worshiper who gives thanks to God for recovery from a deathly illness. Hence there is a bewildering discrepancy between the content and its title as recorded in verse 1...
Sarna, Psalms, p. 149
At some period, the composition was wholly reinterpreted so that the worshiper became the entire community viewed as a collective personality. The implied sickness was understood as a metaphor for a national calamity, and the remarkable recovery was construed in terms of a great experience of national deliverance followed by the joyous rededication of the Temple....
What historic event occasioned this reinterpretation? Two possibilities come to mind. The first is the dedication of the Second Temple...in the spring of 515 B.C.E. As told in Ezra 6:15-18 the entire people "celebrated the dedication of the House of God with joy."
The other possibility...is the purification and rededication of the Temple in the autumn of 164 B.C.E. following the victory of Judah Maccabee over the Syro-Greeks. The events...have been celebrated by Jews ever since in the annual eight-day festival of Hanukkah ("dedication")...The post-Talmudic minor tractate called Soferim prescribes Psalm 30 as a liturgical reading for the festival.
Sarna, Psalms, p. 140
The psalmist is not talking to himself; he is sharing his personal experiences with a group....The religious experience achieves its fullest expression, not in an individual, private setting, but in a public social context.
Sarna, Psalms, p. 145
The "hiding of God's face" is a figure of speech much used in the psalms. It connotes God's self-willed withdrawal of His favor and providential care. This is how the psalmist interpreted his sudden, severe illness.
Sarna, Psalms, p. 144
The "lament" is the dirge, usually intoned over the dead by relatives and friends. Here, the sick psalmist has been reciting it over himself!