Mu'awiyah bin Hakim (may Allah have mercy on him) narrates from his paternal uncle that he said: O Messenger of Allah! I am away from water and my wife is with me; may I have intercourse with her? He (peace and blessings be upon him) said: "Yes." He said: O Messenger of Allah! I stay away for several months (that is, away from home). He (peace and blessings be upon him) said: "Even if you remain (so) for three years." His uncle's name was Hakim bin Mu'awiyah al-Numayri (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 1044