Sayyiduna Jundab bin Sufyan (may Allah be pleased with him) narrates: the Prophet (peace and blessings be upon him) loved to pray tahajjud at night: "Half of it, a third of it, a quarter of it, the time it takes to milk a she-camel, the time it takes to milk a goat."
Al-Tabarani recorded it in al-Mu'jam al-Awsat and al-Mu'jam al-Kabir; its chain contains Abu Bilal al-Ash'ari, whom al-Daraqutni (may Allah have mercy on him) declared da'if (weak).