Sahih Bukhari, Chapter: Knowledge

I saw the Prophet near the Jamra and the people were asking him questions (about religious problems). A man asked, "O Allah's Apostle! I have slaughtered the Hadi (animal) before doing the Rami." The Prophet replied, "Do the Rami (now) and there is no harm." Another person asked, "O Allah's Apostle! I got my head shaved before slaughtering the animal." The Prophet replied, "Do the slaughtering (now) and there is no harm." So on that day, when the Prophet was asked about anything as regards the ceremonies of Hajj performed before or after its due time his reply was, "Do it (now) and there is no harm."