Jabir bin Abdullah (may Allah be pleased with him) says that it never happened that anything was asked from the Messenger of Allah (peace and blessings be upon him), and he said no.

Narrated from Sayyiduna Anas (may Allah be pleased with him) that a man asked the Messenger of Allah (peace and blessings be upon him) for the sheep between the two mountains, so the Prophet (peace and blessings be upon him) gave them to him. He went back to his people and said, "O people! Accept Islam, for by Allah, Muhammad (peace and blessings be upon him) gives gifts without any fear of poverty." Sayyiduna Anas (may Allah be pleased with him) said that a person would become Muslim only for worldly gain, then he would become such a Muslim that Islam would become dearer to him than the whole world. (At first he became Muslim out of greed, but later he became sincere.)