When the former generations of Israelites had heard these commands, they refused to pay attention to the Lord. They turned away from Him stubbornly like a rebellious ox, and they put their fingers in their ears so they would not hear Him. They hardened their hearts (minds and wills) like flint (Heb. shamir, diamond) so they could not hear the Law or the Holy Spirit"s messages through the former prophets whom God had sent to them. [source][source][source]
"This remarkable doctrine of the Holy Spirit as mediator of God"s word to the prophets, who were themselves its mediators, has no parallels in the prophetic books. ...Zechariah is the first to record this aspect of the doctrine of the Spirit." [1][source]
God had proceeded to dull the people"s ears in discipline because they would not hear (cf. Isaiah 6:10; Acts 28:27). Consequently great wrath had come from the Lord against them. [source][source][source]
"One indispensable ingredient in true spirituality is a dogged attentiveness to familiar truths, but they did not "pay attention."" [2][source]