“And the publican, standing afar off would not lift up so much as his eyes unto heaven, but smote upon his breast, saying, God be merciful to me a sinner.”- Luke 18:13

Our Saviour, being desirous of setting before us the necessity of humiliation in prayer, has not selected some distinguished saint who was famed for his humility, but He has chosen a tax-gatherer, probably one of the most extortionate of his class, for the Pharisee seems to hint as much; and I doubt not he cast his eye askance at this publican, when he observed, with self-gratulation, “God, I thank Thee, that I am not as other men are, extortioners, unjust, adulterers, or even as this publican.” Still, our Lord, in order that we might see that there was nothing to predispose in the person, but that the acceptance of the prayer might stand out, set even in a brighter light by the black foil of the publican’s character, has selected this man to be the pattern and model of one who should offer an acceptable prayer unto God…  But so it happened, that the Spirit of the Lord met with the publican; and had made him think upon his ways, and their peculiar blackness: he was full of trouble, but he kept it to himself, pent up in his own bosom, he could scarcely rest at night nor go about his business by day, for day and night the hand of God was heavy upon him. At last, unable to endure his misery any longer, he thought of that house of God at Zion, and of the sacrifice that was daily offered there. “To whom, or where should I go,” said he, “but to God?-and where can I hope to find mercy, but where the sacrifice is offered.”

At last his stifled feelings found utterance; yet that utterance was a groan, a short prayer that must all be comprehended in the compass of a sigh: “God be merciful to me a sinner.” It is done; he is heard; the angel of mercy registers his pardon, his conscience is at peace; he goes down to his house a happy man, justified rather than the Pharisee, and rejoicing in the justification that the Lord had given to him. Well then, my business is to invite, to urge, to beseech you to do what the publican did, that you may receive what he obtained.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0216.cfm