We have seen that the righteousness of which Jesus here speaks refers to that practical obedience to His commands which our Lord said was necessary for admission to the kingdom (5:20). To seek for God’s righteousness, therefore, is a necessary corollary of seeking His kingdom, for He is the righteous King who requires that His subjects obey and imitate their Ruler. Earlier in the Sermon on the Mount, Jesus told His disciples what this sort of righteousness looks like:

Renouncing anger (5:21-26)
Making war on lust (5:27-30)
Remaining faithful to one marriage partner for life (5:31-32)
Avoiding impious and insincere oaths, and speaking simple truth (5:33-37)
Giving to the unworthy (5:38-42)
Loving the unlovely and the unloving (5:43-48)
Giving generously, but in secret, for God’s eyes only (6:1-4)
Praying privately, in faith, to our Father in heaven (6:5-13)
Forgiving our enemies (6:14-15)
Fasting for God’s pleasure alone (6:16-18)
Laying up treasures in heaven, not on earth (6:19- 21)
Worshiping God, not Mammon [money] (6:22-24)
Forsaking all worry as we trust God to provide (6:25-32)

These are the things for which we should hunger and thirst every day (5:6).