ereunaō

The picture behind this word is a thorough pass over something rather than a glance at its surface. You go through the whole of it, part by part, until whatever it holds has come into the open. Greek writers used it of a hound working out a scent and of anyone hunting through a place for what might be hidden there, and that sense of covering the ground completely stays with it in the New Testament.

The word appears six times, and what is being searched is the interesting part:

• the Scriptures, gone over for the life they are thought to hold (John 5:39; John 7:52)
• the prophets' own words, gone over to learn who and when the Spirit meant (1 Peter 1:11)
• the human heart, read by the God who knows what the Spirit is asking for (Romans 8:27; Revelation 2:23)
• the depths of God himself, known from the inside by his own Spirit (1 Corinthians 2:10)

The same act runs through both halves of that list, but who is doing it changes everything. When people search, the outcome is genuinely open: they may find what they are after or miss it completely, which is exactly the sting in John 5:39. When God searches, the word is not saying he is feeling his way toward information he lacks. It is chosen because it describes going all the way through something, and the claim is that nothing in a person, or in God, lies closed off.

A related verb built on this one, meaning "to search a matter out to the end" (ἐξεραυνάω), stands right beside it in 1 Peter 1:10-11: the prophets first search out the rescue they announced, then keep searching to learn its person and its time. Set against the ordinary verb for seeking, ζητέω, this word does not go looking for something absent; it works through something already in hand.