For Greek, you can use
bible.cc/. It has (almost) only Protestant resources but it is still a handy tool. So you can look up
Matthew 16:18 and see all the Greek words in the verse. From there you can access dictionaries and concordances. The entry for
petra in Thayer’s Lexicon makes mention of this controversy.
c. metaphorically, a man like a rock, by reason of his firmness and strength of soul: Matthew 16:18 (some interpretations regard the distinction (generally observed in classic Greek; see the commentaries and cf. Schmidt, Syn., chapter 51, §§ 4-6) between πέτρα, the massive living rock, and πέτρος, a detached but large fragment, as important for the correct understanding of this passage; others explain the different genders here as due first to the personal then to the material reference. Cf. Meyer, Keil, others; Green, Critical Note on John 1:43).
biblesuite.com/thayers/4073.htm
Some of the sources on the site insist on the
petros-
petra distinction, but this is never substantiated from any contemporary literature. Without being a Greek scholar myself, I feel confident in the fact that
petros is not used anywhere in the New Testament in any other sense than the name Peter, that
petros is merely a masculinization of
petra.
