Passage
Why do ye not understand my speech? even because ye cannot hear my word.
John 8:43 (KJV)
Nearby Context
John 8:41 Ye do the deeds of your father. Then said they to him, We be not born of fornication; we have one Father, even God.
John 8:42 Jesus said unto them, If God were your Father, ye would love me: for I proceeded forth and came from God; neither came I of myself, but he sent me.
John 8:43 Why do ye not understand my speech? even because ye cannot hear my word.
John 8:44 Ye are of your father the devil, and the lusts of your father ye will do. He was a murderer from the beginning, and abode not in the truth, because there is no truth in him. When he speaketh a lie, he speaketh of his own: for he is a liar, and the father of it.
John 8:45 And because I tell you the truth, ye believe me not.
Study Lenses
The verse centers on "understand", "speech", "even", "hear", and "word". It is saying that the verse draws attention to "understand" and "speech", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 42's "Jesus said unto them If God were..." into verse 44's "Ye are of your father the devil...", so "understand" and "speech" belong inside that flow. In John context, the local focus is the identity of Jesus, new birth, eternal life, and belief and unbelief.
A plain takeaway is to answer the verse's own emphasis on "understand" and "speech" with trust shaped by these words, not by a vague optimism outside the passage.