If ye love those who love you, what grace have you? for sinners do the same; rather love your enemies, and do good, and lend, hoping for nothing; then shall your reward be great, and ye shall be the sons of the Most High (6:32-35). That man cannot do good that is good from himself, the Lord also teaches in John:

A man cannot take anything unless it be given Him from heaven (3:27). And in another place:

Jesus said, I am the vine, ye are the branches: as the branch cannot bear fruit from itself, unless it shall abide in the vine, so neither can ye unless ye shall abide in Me: He who abideth in Me and I in him, he beareth much fruit, for except from Me ye cannot do anything (15:4-8).