I don’t think people who find things in the Old Testament and say, “Looky here, that’s a sin” fully understand what it means to be Christian. What’s in the Old Testament is just a bunch old Jewish laws. Christians are now ‘above’ the law. Consider that Jesus Christ was completely without sin and yet he frequently and flagrantly broke many of the Old Testament laws. Sinning is not so much what you do but why you do it. Love God more than anything and love your neighbor at least as much as yourself. Do those two things and everything else is pretty much optional.
Prayer is our Christian duty. It is an expression of submission to God and dependence upon Him. For that matter, prayer is arguably the most objective measurement of our dependence upon God. The things you pray about are the things you trust God to handle. The things you neglect to pray about are the things you trust you can handle on your own." H.B. Charles, Jr.