9981. That good must not be done for the sake of a reward, the Lord Himself teaches in Luke:
If ye love those who love you, what thanks have ye? If ye do well to those who do well to you, what thanks have ye? For sinners do the same. Rather love your enemies, and do well, and lend, hoping for nothing; then shall your reward be great, and ye shall be sons of the Most High (Luke 6:32-35).
That a man cannot from himself do good that is good; but only from the Lord, the Lord also teaches in John:
A man can receive nothing unless it be given him from heaven (John 3:27).
Jesus said, I am the vine, ye are the branches; he that abideth in Me, and I in him, the same beareth much fruit; for without Me ye can do nothing (John 15:5).