“Christians must tithe to their local church!”

Christians were never instructed by Jesus or his disciples to tithe. This teaching came many centuries later with the proof text of Malachi 3:8-11

“You are under a curse—the whole nation of you—because you are robbing me. Bring the whole tithe into the storehouse that there may be food in my house.” Malachi 3:8-11

The tithe has been reemphasized in the past three or four decades primarily by evangelical pastors and prosperity teachers, who preach adamantly on one hand that we’re saved by grace and that it’s impossible to fulfill the Law of Moses and on the other insist under much threat of curse on personal goods, finances and lives—one even equated it with salvation, that Christians must follow the Law by tithing.

Curiously, this “Christian” version of the tithe in no way resembles the Levitical tithe or the tithe Abraham gave to Melchizedek but is much more demanding. God commanded the Israelites to tithe food not money and to eat it themselves. (Deuteronomy 12:5-7) Only in the third year were they to give it to the Levites, who were to in turn divide it with the “aliens (immigrants), orphans and widows”. (Deuteronomy. 26:12-13)

Christians are never to be put under the Law! Paul had some scathing things to say about those who attempt to put them there and those who allow themselves to be put under the Law. (Read the book of Galatians).
Read more about "tithing" on my Freeing Truths blog:
http://freeingtruths.blogspot.com/search/label/Tithing%20part%201   http://freeingtruths.blogspot.com/search/label/tithing%20part%202
http://freeingtruths.blogspot.com/search/label/Tithing%20part%203

"To keep praying for something is a lack of faith."

It’s often said in our times, “Pray for something once and let it go. Trust that God heard you and that he will do what’s best for you. To keep on praying for the same thing is a lack of faith—you’ve got to just trust God.” It sounds reasonable. But it’s not what Jesus said.

“Then Jesus told his disciples a parable to show them that they should always pray and not give up. He said: "In a certain town there was a judge who neither feared God nor cared about men. And there was a widow in that town who kept coming to him with the plea, `Grant me justice against my adversary.' "For some time he refused. But finally he said to himself, `Even though I don't fear God or care about men, yet because this widow keeps bothering me, I will see that she gets justice, so that she won't eventually wear me out with her coming!' "And the Lord said, "Listen to what the unjust judge says. And will not God bring about justice for his chosen ones, who cry out to him day and night? Will he keep putting them off? I tell you, he will see that they get justice, and quickly.” Luke 18:1 (emphasis added)

Jesus told us (as his disciples) to keep on praying for the same thing (within Biblical parameters of course) and to not give up until we get it. He wants us to be so engaged with him, so involved in asking him for things that when we get them, there is no doubt that our Father did it!