Sin is separation from God:
Isaiah 59:2
But your iniquities have separated between you and your God, and your sins have hid his face from you, that he will not hear.
Micah 3:4
Then shall they cry unto the LORD, but he will not hear them: he will even hide his face from them at that time, as they have behaved themselves in an evil way in their deeds.
Ezekiel 39:23-24
And the heathen shall know that the house of Israel went into captivity for their iniquity: because they trespassed against me, therefore hid I my face from them, and gave them into the hand of their enemies: so fell they all by the sword. According to their uncleanness and according to their transgressions have I done unto them, and hid my face from them
Isaiah 1:15
And when ye spread forth your hands, I will hide mine eyes from you: yea, when ye make many prayers, I will not hear: your hands are full of blood.
Deuteronomy 31:17-18
Then my anger shall be kindled against them in that day, and I will forsake them, and I will hide my face from them, and they shall be devoured, and many evils and troubles shall befall them; so that they will say in that day, Are not these evils come upon us, because our God is not among us? And I will surely hide my face in that day for all the evils which they shall have wrought, in that they are turned unto other gods.
Proverbs 1:28 CJB and Proverbs 1:29
Then they will call me, but I won’t answer; they will seek me earnestly, but they won’t find me. For that they hated knowledge, and did not choose the fear of the Lord
Isaiah 57:17 ESV
Because of the iniquity of his unjust gain I was angry, I struck him; I hid my face and was angry, but he went on backsliding in the way of his own heart.
Proverbs 15:29
The LORD is far from the wicked: but he heareth the prayer of the righteous.
Deuteronomy 32:19-20 KJ2
And when the LORD saw it, he abhorred them, because of the provoking of his sons, and of his daughters. And he said, I will hide my face from them, I will see what their end shall be: for they are a very perverse generation, children in whom is no faith.
John 9:31 ESV
We know that God does not listen to sinners, but if anyone is a worshiper of God and does his will, God listens to him.
Proverbs 28:9
He that turneth away his ear from hearing the law, even his prayer shall be abomination.
Job 27:8-9 GNV
For what hope hath the hypocrite when he hath heaped up riches, if God take away his soul? Will God hear his cry, when trouble cometh upon him?
Zechariah 7:13 KJ2
Therefore it has come to pass that as He cried and they would not hear, so they cried and I would not hear,” saith the Lord of hosts.
Ezekiel 8:17-18 NLT
Have you seen this, son of man?” he asked. “Is it nothing to the people of Judah that they commit these detestable sins, leading the whole nation into violence, thumbing their noses at me, and provoking my anger? Therefore, I will respond in fury. I will neither pity nor spare them. And though they cry for mercy, I will not listen.
Jeremiah 14:10-12
Thus saith the Lord unto this people, Thus have they loved to wander, they have not refrained their feet, therefore the Lord doth not accept them; he will now remember their iniquity, and visit their sins. Then said the Lord unto me, Pray not for this people for their good. When they fast, I will not hear their cry; and when they offer burnt offering and an oblation, I will not accept them: but I will consume them by the sword, and by the famine, and by the pestilence.
Isaiah 58:9 HCSB
At that time, when you call, the Lord will answer; when you cry out, He will say, ‘Here I am.’ If you get rid of the yoke among you, the finger-pointing and malicious speaking,
Proverbs 21:13
Whoso stoppeth his ears at the cry of the poor, he also shall cry himself, but shall not be heard.
Psalm 66:18
If I regard iniquity in my heart, the Lord will not hear me
Psalm 34:15-16
The eyes of the Lord are upon the righteous, and his ears are open unto their cry. The face of the Lord is against them that do evil, to cut off the remembrance of them from the earth.