Matthew 6:1 says, "Be careful not to do your acts of righteousness before men, to be seen by them. If you do, you will have
no reward from your Father in heaven."
This is right on the heels of Matthew 5:12 (in the same sermon, the one on the Mount), that says, "Rejoice and be glad, because great is your reward in heaven..." This referring to people being persecuted and falsely accused.
Something about rewards that we should know:
1. The Lord rewards (See I Samuel 24:19; Proverbs 25:22; and Colossians 3:24)
2. The Lord rewards according to what we have done
(See Proverbs 19:17; Jeremiah 17:10 and 32:19; and Ephesians 6:8)
3. My reward is with God (See Isaiah 49:4; Matthew 5:12; and Luke 6:23)
Where are you looking for your rewards? Your reward is with God, your reward is God.