Psalms 66:18

¹⁶ Come and listen, all you who fear God, and I will declare what He has done for me.

¹⁷ I cried out to Him with my mouth and praised Him with my tongue.

If I had cherished iniquity in my heart, the Lord would not have listened.

¹⁹ But God has surely heard; He has attended to the sound of my prayer.

²⁰ Blessed be God, who has not rejected my prayer or withheld from me His loving devotion!

Do read the surrounding verses too, because the context often says more than a single verse.

Compare

BSB: If I had cherished iniquity in my heart, the Lord would not have listened.
KJV: If I regard iniquity in my heart, the Lord will not hear me:
WEB: If I cherished sin in my heart, the Lord wouldn’t have listened.
ASV: If I regard iniquity in my heart, The Lord will not hear:
DARBY: Had I regarded iniquity in my heart, the Lord would not hear.
BLB: If I had seen iniquity in my heart, the Lord would not have listened.

John 9:31
We know that God does not listen to sinners, but He does listen to the one who worships Him and does His will.
Read in context
Proverbs 28:9
Whoever turns his ear away from hearing the law, even his prayer is detestable.
Read in context
Proverbs 15:29
The LORD is far from the wicked, but He hears the prayer of the righteous.
Read in context
Proverbs 15:8
The sacrifice of the wicked is detestable to the LORD, but the prayer of the upright is His delight.
Read in context
Isaiah 1:15
When you spread out your hands in prayer, I will hide My eyes from you; even though you multiply your prayers, I will not listen. Your hands are covered with blood.
Read in context
James 4:3
And when you do ask, you do not receive, because you ask with wrong motives, that you may squander it on your pleasures.
Read in context
Proverbs 21:13
Whoever shuts his ears to the cry of the poor, he too shall cry out and receive no answer.
Read in context
Job 27:8–9
For what is the hope of the godless when he is cut off, when God takes away his life?
Read in context