Sahih Muslim Book 6, Hadith Number 2390.

Chapter : The month may consist of twenty-nine days.

Muhammad b. Sa’d reported on the authority of his father (Sa’d b. Abi Waqqas (Allah be pleased with him) that the Apostle of Allah (may peace be upon him) had said: Two month is thus and thus, and thus, i.e. ten, ten and nine. This Hadith has been narrated by Abu Khalid with the same chain of transmitters.