Figure out if it is simple
muscle soreness or if it is pain caused from some type of injury. If it is not an injury, then he should start out a bit slower. When everyone gets to the gym for the first time after a long layoff they tend to go all out. Your body isn't ready for this kind of assault. Do only a few sets for each body part. I realize that he may feel that he can do more, but his body will reject the extra work later on. Make sure he gives his body a chance to get used to being worked again. After a few weeks he can SLOWLY increase the work load as his body gets used to the strain of working out. Don't forget that a workout is an incredible amount of stress to put the body through. The supps that Steve suggested are also essential to helping the recovery process. He might wish to add some Vitamin E, also (800mg/day).