Mark 12:41–44 (CSB)
41 Sitting across from the temple treasury, he watched how the crowd dropped money into the treasury. Many rich people were putting in large sums.
42 Then a poor widow came and dropped in two tiny coins worth very little.
43 Summoning his disciples, he said to them, “Truly I tell you, this poor widow has put more into the treasury than all the others.
44 For they all gave out of their surplus, but she out of her poverty has put in everything she had—all she had to live on.”
The gift of salvation from God is free.
Titus 3:4-7 (CSB) But when the kindness of God our Savior and his love for mankind appeared, he saved us —not by works of righteousness that we had done, but according to his mercy — through the washing of regeneration and renewal by the Holy Spirit. He poured out his Spirit on us abundantly through Jesus Christ our Savior so that, having been justified by his grace, we may become heirs with the hope of eternal life.
Romans 6:23 (CSB) For the wages of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.
But when you receive this gift, it will cost you everything.
Your sin, your heart, your thinking, your soul, your affections, your actions--they now belong to God.
1 Corinthians 3:21-23 (CSB) So let no one boast in human leaders, for everything is yours — whether Paul or Apollos or Cephas or the world or life or death or things present or things to come — everything is yours, and you belong to Christ, and Christ belongs to God.
1 Corinthians 6:19-20 (CSB) Don’t you know that your body is a temple of the Holy Spirit who is in you, whom you have from God? You are not your own, for you were bought at a price. So glorify God with your body.
So let us not read this passage and think, "If we give like the poor widow, we will have God."
No. Where God leads us to give--not out of obligation nor guilt nor shame--we give because our money is not ours but God. God provides for all of our needs.. Our affections and desires are not ours but God's. God has given us his heart so that we would have new affections and desires for him.
Even our thinking belongs to him:
2 Corinthians 10:5b (CSB) we take every thought captive to obey Christ.
God wants everything from us because in Christ, he has given us everything.