Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Whoever fights in the way of Allah for as long as the interval of milking a she-camel, Paradise becomes obligatory for him."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18559