If you are in Group 2, you will take 3 capsules of ibrutinib by mouth 1 time every day with 1 cup of water. Your doctor will tell you if you will start taking the ibrutinib on Day 1 or Day 2 of Cycle 1. You will receive rituximab by vein over between 3 and 8 hours on Days 1, 8, 15, and 22 of Cycle 1, then on Day 1 of Cycles 2-6.