Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) said: "How much of the month has passed?" They said: Twenty-two have passed and eight remain. He (peace and blessings be upon him) said: "Rather, twenty-two have passed and seven remain; so seek it tonight."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8539