The grandson of Sayyiduna Bayharah bin Amir (may Allah be pleased with him) narrates from his father, who heard his own father (Bayharah, may Allah be pleased with him) say: We came to the Messenger of Allah (peace and blessings be upon him) and accepted Islam, and we asked him to excuse us from the Isha prayer. He (peace and blessings be upon him) said: "The Isha prayer?" We said: We are busy milking our camels. He (peace and blessings be upon him) said: "In sha' Allah, you will milk and you will pray as well."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1229