My friend did an intense ab workout this morning, and now his lower abs are extremely sore. is there anything he can do or take to relieve the pain sooner than later? thank you.

Exercise: Consider lots of water. Stay hydrated & avoid alcohol. These may help lactic acidosis.

Yeah, not be so craz: He almost certainly "pulled" his abdominal wall musculature. If it's really painful than he may have actually torn the muscle and that would take much longer to fully recover. He could use physical therapy too and depending how severely he was damaged he might need intervention by a sports medicine orthopedist.

H2O & Essential Oils: After an intense workout, the muscles experience lactic acid accumulation. This can contribute to muscular aches/pain/soreness. In order to help alleviate the lactic acidosis, one should hydrate before, during and after exercise. There are some effective essential oils that can be used: Marjoram Deep Blue (oil blend by DoTerra)

Water and time: Your friend needs to drink plenty of water and may want to take over the counter medications like ibuprofen or acetaminophen if they do not have allergies to these medications. The muscle will feel less sore over time. But if the pain is severe there maybe something else going on and your friend should see a physician.