The correct postoperative instruction after a vasectomy is to apply ice and rest. This helps to reduce swelling and pain in the scrotal area, minimizing inflammation and promoting healing. Patients are advised to avoid strenuous activities and heavy lifting initially to prevent complications such as hematoma or increased bleeding. Proper scrotal support and rest aid in comfort and faster recovery. Immediate heavy exercise can increase the risk of discomfort and postoperative complications. Routine antibiotics are not generally required unless there is an infection.

Reference: Sabiston Textbook of Surgery, 21st Edition.