Musnad Ahmad

It is narrated from Hazrat Abu Umamah (may Allah be pleased with him) that once we set out with the Noble Prophet (peace and blessings be upon him) for a jihad. A man passed by a cave where there was some water. He thought to himself that he should settle in that cave, sustain his life with the water present there, eat the vegetables growing nearby, and adopt seclusion from the world. Then he thought that first he should present this matter to the Noble Prophet (peace and blessings be upon him); if he granted permission, he would do so, otherwise not. So he came to the Noble Prophet (peace and blessings be upon him) and said, "O Messenger of Allah! I passed by a cave in which there is enough water and vegetables for my sustenance. I have thought of settling there and withdrawing from the world." The Noble Prophet (peace and blessings be upon him) said, "I have not been sent with Judaism or Christianity; I have been sent with the pure, upright religion of Hanifiyyah. By the One in whose hand is the life of Muhammad (peace and blessings be upon him), going out in the way of Allah in the morning or evening is better than the world and whatever is in it, and for any one of you to stand in the ranks of jihad is better than sixty years of prayer."