Thought From Today’s Old Testament Passage:
[Psalm 78] The supreme quantity of this psalm is that throughout all its measures, over against the repeated failure of His people God’s persistent patience is set forth in bold relief. The purpose of the psalm, however, is to warn God’s people against unfaithfulness by the story of past failure. After announcing his determination the first eight verses declare the purpose of the singer. Things of the past are to be recounted for the sake of the children. Notice very carefully the statement of the latter part of this introduction. It announces the institution in Israel of a method for dealing with the children. The words “testimony” and “law” (verse 5) do not here refer to the Mosaic economy, but to a specific arrangement for transmission of that law. This arrangement was to instruct the children. The value of such instruction was that the new generation would be safeguarded in its hope, its memory, and its conduct.
…It would seem almost past belief to us as we read that a people so led could forget. Yet is not this sin of forgetfulness with us perpetually? In some day of danger and perplexity we become so occupied with the immediate peril as utterly to fail to think of past deliverances. Such forgetfulness is of the nature of unbelief in its worst form. It wrongs God and paralyzes our own prayer.
G. Campbell Morgan, An Exposition of the Whole Bible (Fleming H. Revell Company, Westwood, NJ, MCMLIX), page 249-250