God gives his people clear direction as to how they should use their time and money. As regards the former, God says,
Remember the Sabbath day, to keep it holy. (Exodus 20:8)
As for the latter, God often instructs his people to offer a tenth of some good that he has provided (e.g. their harvest, livestock; see Numbers 18:21; Leviticus 27:30-33; Deuteronomy 14:22-27; Malachi 3:6-12).
Very sincere and smart Christians disagree with me, but I don't believe Christians are required to rest on Saturdays (or Sundays, for that matter). Nor are they obligated to give a tenth of their finances to the church. The New Testament does not enjoin Sabbath observance, as the fourth commandment is not repeated in the New Testament (interestingly. the other 9 commandments are). Moreover, no New Testament author prescribes tithing for Christians. NT passages that mention tithing are descriptive, rather than prescriptive.
The New Testament's silence on these matters is attributable to its place in redemptive history. Jesus comes to fulfill the Old Testament Law (Matthew 5:17-20).. Jesus fulfills the law by clarifying its intent, intensifying it, and obeying it perfectly on our behalf. That means we should view the entirety of OT law through the interpretative lens Christ provides. Not everything in the OT carries over into the NT.
Tithing existed (in large part) to support the Levitical priesthood. But this priesthood has been fulfilled and superseded by the priesthood of Jesus (see Hebrews 7). We don't give Jesus a tithe (we give him everything!). As for the Sabbath, it was a weekly reminder of Israel's need to rest in God's provision and protection. But Jesus is our eternal provision and protection. He freely offers us the rest we need; the spiritual rest which Israel's Sabbath observance foreshadowed (see Hebrews 4).
When Christ comes, he inaugurates the New Covenant. This covenant fulfills and replaces the Old Covenant. The New Covenant is characterized by grace. God's grace was apparent in the Old Testament, but in Jesus, we receive (as John says), "grace upon grace" (John 1:16-17). We experience a measure of grace that the OT saints could only hope for (Hebrew 12). And this New Covenant grace should make us radically generous (2 Corinthians 8:1-5) and radically restful (Hebrews 4:1-11).
With that biblical groundwork established, here's the sad irony I find in my life, and the lives of so many Christians. God's grace actually makes us less generous and restful, not more.
You're not obligated to give 10% of your money to the church. Do you hear that and think, "phew, I get to keep more of my money"?
You don't have to rest on Saturday (or Sunday). Do you hear that and think, "phew, I can get more done"?
If God's grace is more powerfully active in God's people after Christ's coming than before, shouldn't that affect us? And specifically, shouldn't it make us more generous, and more restful than the Israelites? Shouldn't we view 10% as a starting point for generosity, rather than an unattainable goal? Shouldn't we be eagerly looking for new ways to rest in Jesus; to enjoy the grace he gives, and to "waste time" with God's people? If our positional rest in Jesus doesn't translate to actual rest during the week, something has failed to register.
Americans worship money and work. It's not a stretch to say those gods are perched atop our national pantheon. Two of the clearest ways to renounce those gods (and worship the true God) are by (1) being radically generous, and (2) being radically restful.
The gospel isn't license; it's liberating power.
The Father gave you his Son. He's already met your deepest need; can't you trust him with every other need (Rom 8:32)? With that kind of God as your dad, you can be radically generous with your money.
And you can rest from work, knowing that God ultimately provides for your needs. Furthermore, you can rest from work because you don't have to work for an identity. Your identity is rooted in Christ's performance, not yours. God didn't adopt you into his family because you had a great work ethic, or because you were a team player who could make real and lasting contributions to the Trinity. God adopted you because he delighted in you; because he wanted you. You already have an identity you can't earn. So relax! Rest! Stop trying to prove yourself by working all the time.
At root, our restlessness and miserliness are gospel problems. Thus, they need gospel solutions.
So, let's make this practical:
If you aren't generous, ask yourself; "do I really believe that God is good? Do I really believe that he withholds no good thing from me? And do I really trust that he will be good to me, even when giving is costly?"
If you aren't generous, repent of your unbelief, and rejoice that God continues to give himself to you even thought you don't give yourself to him, or your stuff to others.
If you aren't at rest, ask yourself; "do I really believe that God is gracious? Do I really believe that my identity is secure in him, and that I don't have to prove myself through hard work? Do I believe that it's ok to rest, because I really am ok with God?"
If you aren't restful, repent of your unbelief, and rejoice that God continues to delight in you, even though you refuse to rest in him, and continue trying to prove yourself through performance.