John 5:39

ἐραυνᾶτε τὰς γραφάς, ὅτι ὑμεῖς δοκεῖτε ἐν αὐταῖς ζωὴν αἰώνιον ἔχειν· καὶ ἐκεῖναί εἰσιν αἱ μαρτυροῦσαι περὶ ἐμοῦ

You search the scriptures, because you believe in them to have eternal life, and/but it is they which testify about me


 * The gender of the antecedent controls the gender of subsequent pronouns and referrents. Hence the antecedent τὰς γραφάς is feminine and so αὐταῖς, ἐκεῖναί, αἱ μαρτυροῦσαι are all feminine. Useful. In English we get "they ... they ... they" and sometimes get lost as to what the last they refers to.
 * ἐραυνᾶτε - is an interesting word. The ἐ is not an augment, neither that nor the τε indicates an aorist. As a lexical form, it is a word which begins with ἐ. The stem also ends with α, so with the present active personal ending α + ετε, α + ε contracts to ᾶ, with the handy circumflex about to indicate a contraction. So the word is actually a present active indicative 2 person plural.
 * ἔχειν - to have. This is an infinitive. It gives more information about the verb δοκεῖτε (you all think, believe). What is it you all believe? You believe that ... to have....
 * περὶ ἐμοῦ - ἐμοῦ is genitive. περὶ + genitive = about: about me. See περί for more.