In this excerpt from the Padma Purana, in a chapter which I think is likely an interpolation, Shiva comes to Rama's court disguised as a Brahmana and tells Rama how you can derive omens by picking verses from a Purana and interpreting their significance in light of whatever problem you're trying to solve. Rama asks what happens if you don't understand a meaning of a particular verse, and Shiva says this:
The meaning of the verse: Madhuni ca madhunyatra madhurmadhubhujam madhuh; madhuna madhunadyartham visani ca visani ca is unintelligible; it is not recommended in (finding out) an omen. So also the verse: Ruti rute rute rorauriri raram rari-raram; evam karoti suddhatma brahmano brahmanotithih. This verse is intelligible in part (the latter half is intelligible: a pure-souled brahmana, the guest of Brahman, acts like this). (Therefore) it is not recommended in (finding out) an omen. O best of the Raghus, such and other verses occur in the Puranas. They have no explanation.
Now Rama ultimately uses this method to find out that Vibhishana has been tied up in Sri Rangam for killing a Brahmana, and he rescues Vibhishana. But my question is, which Puranas do the so-called unintelligible "Madhuni ca" and "Ruti rute" verses mentioned by Shiva come from?
Shiva says that the two best Puranas for deriving omens are the Skanda Purana and the Vishnu Purana. But so far I haven't found either verse outside of the Padma Purana.
Also, is it really hopeless to try to understand these two verses? Madhu means honey, so is it possible that the verse is talking about honey? It might be connected to the Madhu Vidya found in the Upanishads, which I discuss here and here.