"They (Macedonian churches) gave as much as they were able, and even beyond their ability." (II Corinthians 8:1)
A little girl decided that she was going to give her father a pair of slippers for Christmas. A friend asked her, "Where will you get the money from?" She opened her eyes like saucers, and said "Why, Daddy will give me the money." For a moment her older friend was silent as he thought how the dear man would buy his own Christmas present.
The father loved his little girl for the gift even though he had to pay for it himself. The precious little girl didn't have anything in the world except what her father had given her.
So too, you and I have nothing of our own we can give to God. We can only give back to him what belongs to him. Yet, he accepts it!