The Companions (RA) asked the beloved Prophet (PBUH) : "What is the reality of Sacrifice?"
Beloved Prophet (PBUH) Answered : "This is a Sunnah of your father Ibraheem (AS)".
Source : Ashrafia (Khutbat-e-Hakim-ul-Ummat, Sunnah of Ibraheem, Lecture Delivered by Hazrat Maulana Ashraf Ali Thanwi (RA) at Kairana, Muzaffar Nagar, on 24 Zi-Qadah, 1335AH and published in the Periodical Imdad, Lahore, Zi-Qadah 1421AH, February 2001AC, p.35)