Sayyiduna Ibn Umar (may Allah be pleased with them both) narrates from the Noble Prophet (peace and blessings be upon him) that he (peace be upon him) said: "A month can also be of twenty-nine days." And he (peace be upon him) folded his thumb. Therefore, do not begin fasting without sighting the moon, nor stop fasting without sighting the moon. Then, if the moon is concealed from you by clouds, then estimate its count."