Hazrat Umar bin Abdullah Mawla Ghafrah (may Allah have mercy on him) narrates that a son of Hazrat Abdullah bin Umar (may Allah be pleased with them both) spent thirty days in jihad. When he returned, Hazrat Ibn Umar (may Allah be pleased with them both) said to him, "I swear to you that you must go back and spend ten more days in jihad so that forty days are completed."