It is reported from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) recited qunut for a month, then abandoned it. Abd al-Rahman says: He (peace and blessings be upon him) only abandoned the supplication against them.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3103