"Praying for you Joe," one of his followers commented on the post.
"You got this!" another fan remarked.
Earlier this week, Joe's rep confirmed to ET that he had surgery after being diagnosed with prostate cancer two months ago. "This is a blessing in disguise for Joe," a source close to Joe, 58, told ET on Monday. "It has opened his eyes to eating healthier and exercising. This diagnosis has brought Joe and his family together and reminded him that what matters most is family."
As for Jessica and Ashlee, the source said the sisters were "devastated at the initial diagnosis," but have since rallied behind their dad. "They are being positive, uplifting forces for him and are helping him get through this," the source added. "With Joe's faith in God and his family's support, he knows he will come out of this strong."