The backslider in heart—he who turns away from God (Psalms 44:18)—shall be filled with his own ways, shall reap the fruits of his evil doings (Proverbs 1:31; Proverbs 12:14). Matthew 6:2, "Verily I say unto you, they have their reward."
And a good man shall be satisfied from himself. There is no verb expressed in this clause, "shall be satisfied" being supplied by our translators. Delitzsch and others read, "and a good man from his own deeds."
It is simpler to repeat the verb from the former clause: "A good man shall be filled with that which belongs to him;" i.e. the holy thoughts and righteous actions in which he delights. Isaiah 3:10, "Say ye of the righteous that it shall be well with him; for they shall eat the fruit of their doings."
The Vulgate, neglecting the prefix, translates, "And over him shall be the good man;" Septuagint, "And a good man from his thoughts," the produce of his heart and mind.