Will God take out a believer who keeps sinning knowingly?
Yes. The Lord reserves the prerogative to take out a believer who will not shape up and continues in known sin, because He will not let anyone drag His name through the mud. If a professing believer is not chastised, Paul teaches in Hebrews that they are not His children.
Les explains that it is not our prerogative to pray for God to take someone out, but the Lord does have that prerogative. If a believer will not shape up and continues to walk in known sin, then yes, God will take them, because He is not going to let anybody drag His name through the mud. Les also notes that people who have made a profession of salvation and been church members may do the same. If the Lord does not deal with them or chastise them, then Paul teaches in the book of Hebrews that they are not His children. In illustration, if a church member runs off with some young woman and leaves their family, the answer is that they never were saved; if they were saved and did something like that, God would take them out. This is what it means when Scripture says many are sickly and many are already asleep—they died.