Mar 12:41 Now Jesus sat opposite the treasury and saw how the people put money into the treasury. And many who were rich put in much.
Mar 12:42 Then one poor widow came and threw in two mites, which make a quadrans.
Mar 12:43 So He called His disciples to Himself and said to them, “Assuredly, I say to you that this poor widow has put in more than all those who have given to the treasury;
Mar 12:44 for they all put in out of their abundance, but she out of her poverty put in all that she had, her whole livelihood.”

When pastors preach on Mark 12:41-44 (or Luke 21:1-4) it is usually in the context of church offerings. The widow is shown as a truly righteous person to be emulated. They say, give as the widow gave. In this passage the widow gives over “her whole livelihood”. One Sunday, I was pleasantly surprised when one guest pastor pointed out his own error on this teaching. It takes humility to publically point out one’s own faults.

The point Jesus is making is not to give substantial amounts of money to the church. In the Luke passage the arbitrary chapter break muffles the context, but in both parallel passages it is clear: Jesus is condemning people who try to guilt people into giving money:

Mar 12:38 Then He said to them in His teaching, “Beware of the scribes, who desire to go around in long robes, love greetings in the marketplaces,
Mar 12:39 the best seats in the synagogues, and the best places at feasts,
Mar 12:40 who devour widows’ houses, and for a pretense make long prayers. These will receive greater condemnation.”

So Jesus teaches about religious teachers who devour widow’s houses, and then illustrates his point with a real life example. This is not Jesus saying to give all you have to the church. When Jesus tells people to divest their property, he tells them to give it to the poor, see Mat 19:21 (not the government and not the church).