Why do ye not understand—come to appreciate and penetrate the significance of—my speech? There is delicate subtle distinction between λαλιά and λόγος, corresponding to that between λαλέω and λέγω.
The former word connotes the form, manner, and tone of utterance, and the latter its inner substance and power. λαλιά is a, word used for any manifestation of sound, a voice, the babble of children, the cries and songs of beasts or birds, for which purpose λὲγω and λόγος are not used (Trench, 'Syn.
of N.T.'). Peter's λαλιά betrayed him to the Jerusalem crowd (Matthew 26:73). λόγος is the substance of the message, the burden of the revelation. The speech ( λαλιά) of Christ refers to the appropriate and significant clothing which he gave to his word ( λόγος).
He mournfully asks why they had failed to get to understand the method of his converse; why they perpetually failed to appreciate his discourse; why they persistently put wrong constructions upon his phrase, and imagined him to be speaking of earthly things when he was discoursing to them of heavenly ones.
Why? Because ye cannot hear my word—the Divine communication I have made to you. They were morally so far from him that they could not listen so as to receive his revelation. The inward organ of receptivity was lacking, and "so the spiritual idiom in which he spake was not spiritually understood" (Alford).
The Divine significance of the whole word of Christ, the new and strange doctrines of Messiah, of redemption, of the Father, of a sacrifice and death on the part of the Son of man for the salvation of the world excited their animosity and bitter antipathies.
They were not conscious of any of the need he came to satisfy, and so they failed to apprehend the entire manner of his revelation. They were from beneath (John 8:23). He is disclosing heavenly things.
"Their ears have they closed, lest they should hear."