‘Arise, O YHWH. Confront him, make him bow down,
Deliver my soul from the unrighteous by your sword,
From men by your hand, O YHWH,
From men of the world, whose portion is in this life,
And whose belly you fill with your treasure.
They are satisfied with children,
And leave the rest of their substance to their babes.'
‘Arise, O YHWH. Confront him, make him bow down.' He calls on YHWH to awaken to the situation, and to face up to ‘the lion', confront him and bring him down to the ground. Let him be rendered powerless. Let YHWH's sword deliver him from the unrighteous, those who contrary to God's will seek to bring him down. Let His hand save him from the men who come against him.
‘From men of the world, whose portion is in this life, and whose belly you fill with your treasure. They are satisfied with children, and leave the rest of their substance to their babes.' He sums up the unrighteous. They are men taken up with the world (compare John 15:19; Philippians 3:19), men whose sole portion is in this life, (they have no portion in God - contrast Psalms 16:5), their only aim being to bear sons to perpetuate their name and to pass down what they have built up to their children. Thus they ignore God and His ways, their lives are meaningless and inward-looking, and their lives can be summed up in their children and so on ad infinitum. They live a purposeless existence.
And all this in spite of the fact that it is YHWH who supplies them with good things, fills their bellies with treasure, making His rain fall equally on the unrighteous (Matthew 5:45) in order to provide them with the treasures of the harvest.
Or ‘bellies filled with His treasure' might refer to the children in the wombs of their wives, their wives' bellies being seen as their own.
The whole picture of the unrighteous is of meaninglessness of existence rather than of positive evil. They fail to do the good required by God's Law. They fail to love their neighbours as themselves. They fail to truly worship God. They fail in all that is most important.