In proclaiming this, note carefully that Jeremiah is relating something God said to him. Before you even speak, pause. Pause longer than you think is necessary. Then say the first sentence solemnly:
But then follow two rhetorically tortured sentences that will challenge your skills as a public speaker. The author says that the prophets of old struggled with the mystery of the coming Christ, and realized that they were doing so for the benefit of the later generations that would finally come to know Christ. Or, from the opposite point of view, the early Christians would interpret the words of the ancient prophets to make clear Christ's puzzling death and astounding resurrection. So simply stated, that's fairly clear.
However, the two sentences that you have to read aloud have forty-eight words each. You have to break them down for the listeners by your phrasing and by changes of pitch. The verbs governing the first sentence are "searched and investigated." What results from the search and investigation? Something "was revealed," the verb governing the second sentence.
Print out the text of the reading, double-spaced, and mark it up. Enclose logical phrases within nested brackets. Underline and use check marks. Do whatever it takes to make clear to yourself the structure of these sentences. Rehearse before a friend, family member or your parish's coordinator of lectors, until the one listening can "get it" without benefit of a missallette.
What did the author want for his addressees, and what you might hope for yours? I submit that the goal should be a sense of privilege, that people hearing these words feel singled out for a special blessing not enjoyed to other worthy creatures. Two clues support this: The ancient prophets who learned in advance about Christ did so in order that their prophecies would later bolster our faith. And even angels have longed to hear the good news we have heard.