It is narrated from Ikrimah (may Allah have mercy on him) that the Messenger of Allah (peace and blessings be upon him) passed by a man or a woman who was not putting the nose on the ground in prostration, and he (peace and blessings be upon him) said: "Allah Almighty does not accept a prayer in which a person's nose does not touch what his forehead touches."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2654