The main purpose behind sacrifice is to obtain His closeness and pleasure. As it is related by SayyidahAyshah (ra) that the Messenger of Allah (saws) said: "On the 10th of ZulHijjah, i.e., the day of EidulAdha, no act of son of Aadam is more pleasing to Allah than qurbani. On the Day of' Judgement, the animal of qurabani, will come with its horns and hooves.
http://ummid.com/news/2011/November/01.11.2011/sacrifice_and_its_impact.htm
http://ummid.com/news/2011/November/01.11.2011/sacrifice_and_its_impact.htm
