Musnad Ahmad 28:238

Al-Husayn ibn Muhammad and Surayj narrated to us, they said: Ibn Abi al-Zinad narrated to us, from Abd al-Rahman ibn al-Harith, from Amr ibn Shu’ayb, from his father, from his grandfather: That the Messenger of Allah (peace and blessings of Allah be upon him) caught up with two men who were tied together, walking to the House (the Kaaba). The Messenger of Allah (peace and blessings of Allah be upon him) said: "What is the matter with this tying together?" They said: "O Messenger of Allah, we vowed that we would walk to the House tied together." The Messenger of Allah (peace and blessings of Allah be upon him) said: "This is not a vow," and he cut their tie. Surayj said in his narration: "The vow is only that by which the Face of Allah the Almighty is sought."