In Mark chapters 11 and 12 we read of Jesus who had gone into the temple and had been quizzed by various of the scribes, Pharisees and Sadducees. After he had answered them factually and they had no more they could try and pin him with, in chapter 12, Mark tells us this:
"And Jesus sat over against the treasury, and beheld how the people cast money into the treasury: and many that were rich cast in much. And there came a certain poor widow, and she threw in two mites, which make a farthing. And he called unto him his disciples, and saith unto them, Verily I say unto you, That this poor widow hath cast more in, than all they which have cast into the treasury: For all they did cast in of their abundance; but she of her want did cast in all that she had, even all her living."
This one statement shows several of Jesus' observations and we may know that God (Jesus) now observes the same in us. But you can see that he saw who did the contributing, how much they contributed and how it was related to personal sacrifice. In Hebrews 4:31, we have the reminder that all things are 'naked and opened unto His eyes'. So, he knows when we contribute despite the fact we need the funds. And he knows when we do not give even though we have an abundance...more than we actually need.
And we are warned of giving to be seen of men, in Matthew 6:1-4 as was the motive of many of the Pharisees, and is of many today. Read the referenced scripture and you will see.
Even under the Old Testament Law, they were warned for their stingy giving:
"Will a man rob God? Yet ye have robbed me. But ye say, Wherein have we robbed thee? In tithes and offerings." (Malachi 3:8 KJV)
And even though the poor widow gave much less than the wealthy, her sacrifice was far greater than theirs as Jesus plainly mentions. He refers to theirs as coming from their abundance or excess. In other words they had no need for what they gave, yet the widow gave of her want. She needed the money for sustenance but was willing sacrifice it to obey the will of God.
When we are called upon to contribute to the cause of Christ, it doesn't mean just our loose change which is over and above our true need. The apostle Paul tells us plainly in 1 Corinthians 13:1-3, that all of our works are worthless if we do not have charity (love).
It all boils down to the fact our hearts must move us to do the right thing, what ever it takes...effort...sacrifice.