“His lord said to him, ‘Well done, good and faithful servant; you have been faithful over a few things, I will make you ruler over many things. Enter into the joy of your lord.'” Matthew 25:23
Your labor is not in vain. People who are faithful in doing good for God, receive not only the fruit of their efforts but also have a reward that comes directly from God. The joy of the Lord is imparted to the faithful.
This is important because the work of a servant of God is not always easy. There are persecutions, rejections, opposition, sacrifices… in all these things we are more than conquerors through His great love and we have His joy to cause us to overcome all evil.
This is great reward.