Mark 12:41-44 (NIV)
41 Jesus sat down opposite the place where the offerings were put and watched the crowd putting their money into the temple treasury. Many rich people threw in large amounts.
42 But a poor widow came and put in two very small copper coins,worth only a fraction of a penny.
43 Calling his disciples to him, Jesus said, "I tell you the truth, this poor widow has put more into the treasury than all the others.
44 They all gave out of their wealth; but she, out of her poverty, put in everything—all she had to live on."
“But our rewards will be eternal not temporal. “
Yes and no. The primary rewards are eternal.
But don’t forget Matt 19 where the disciples told Jesus they had given up everything to follow Him. He said they would receive all that and much more, in this life and the next. This was a consistent theme in the OT as well.
As for the widow, she gave out of her poverty, but we are promised that God would open the windows of heaven and pour out blessings when we give tithes and offerings.
God does not like to be in debt to anyone. The OT says, “Who has ever given to God and God has owed him the debt?”