For Jesus’ commentary on this parable, see 6:20-26 (the Beatitudes), part of the Sermon on the Plain. [ Blomberg] In the story of the Sermon on the Mount (Matthew 5:20), Jesus says “For I tell you, unless your righteousness exceeds that of the scribes and Pharisees, you will never enter the kingdom of heaven”.

Luke and Paul differ as to who is righteous. While Paul relates righteousness to faith, the law and the cross, Luke emphasizes three points:

self-confident boasting of one’s own good deeds will not achieve acquittal at God’s judgement;
like Jesus, one must engage in deeds of righteousness, e.g. almsgiving;
God has vindicated his innocently suffering righteous one, Jesus the Christ: see 23:47; Acts 3:14; 7:52; 22:14. [ NJBC]
Verse 10: The hours of prayer were 9 am and 3 pm. [ JBC]

Verse 10: “tax collector”: Publicani were tax-farmers who bid on contracts to collect taxes in the provinces. “These publicani paid the stipulated sum-total of the impost directly into the Roman treasury and recouped themselves in the provinces by means of their trained staffs of collectors." [M. Cary and H. H. Scullard, A History of Rome Third Edition, Basingstoke: Macmillan, 1975, 1979]. In essence, having paid the tax up front, they subsequently extorted what they could from the populace, keeping the difference as profit.

Verse 11: “standing by himself”: Jeremias, the great interpreter of the parables, wrote, based on its Aramaic background, that this phrase can be translated: took up a prominent position. [ JBC]

Verse 11: In Matthew 6:5, Jesus says: “... whenever you pray, do not be like the hypocrites; for they love to stand and pray in the synagogues and at the street corners, so that they may be seen by others...”. See also Mark 11:25. [ NOAB] The Law permitted a righteous Jew to disdain the unrighteous. In a standard prayer, then and now, a pious Jewish man thanks God that he is not a slave, a Gentile or a woman ( Babylonian Talmud: Menahot Tractate 43b). Paul’s reaction to this prayer is “There is no longer Jew or Greek, there is no longer slave or free, there is no longer male and female; for all of you are one in Christ Jesus” (see Galatians 3:28). [ Blomberg]

Verse 12: “I give a tenth ...”: See also 11:42. Didache 8:1 says “But as for your fasts, let them not be with the hypocrites, for they fast on the second and fifth days of the week, but fast on the fourth and sixth days”. Christians are bidden to fast on Wednesdays and Fridays. [ BlkLk]

Verse 13: “beating his breast”: After Jesus dies, the crowd “returned home, beating their breasts” ( 23:48). Normally only women beat their breasts; in times of extreme emotion, men did it too. [ NJBC]

Verse 14a: “justified”: This saying of Jesus led to Paul’s doctrine of justification. [ JBC]

Verse 14b: After telling the Parable of the Lost Sheep, in 15:7 Jesus says: “... there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance”.

Verses 15-17: In contrast to the boasting Pharisee of vv. 9-14, disciples (followers) should approach God as a little child: with spontaneity, a spirit of dependence, a sense of wonderment, with no plaques of achievement. The doors of the Kingdom do not swing open to those who comport themselves differently. [ NJBC]