This act of ‘Udhiya’ is to commemorate the unparalleled sacrifice offered by the Prophet Ibrahim . When he, in pursuance to a command of Allah Ta’ala conveyed to him in a dream, prepared himself to slaughter his beloved son Ismail and actually did so, but Allah Almighty after testing him of his submission, sent down a ram and saved his son from the logical fate of slaughter. It is from that time onwards that the sacrifice of an animal became an obligatory duty to be performed by every well to do Muslim.
Concerning this incident the Glorious Quran says:
“And when he attained the age of running with him (Ibrahim), he said: “O my son verily I have seen in a dream that I am slaughtering thee, so look, considerest thou?” He said: “O my father! Do that which thou art commanded, thou shalt find me, Allah willing, of the patients.”
“Then when the two submitted themselves and had prostrated him on his temple.”
“We cried unto him: “O Ibrahim! Of a surety thou hast fulfilled the vision. Verily We! That was a trial manifest. And We ransomed him with a mighty victim. And We left for him among the posterity. Peace be unto Ibrahim. Verily We! Thus we compense the well doers. Verily he was one of Our believing bondsmen.” (37:102-111)
Thus this very incident is also the origin of ‘Takbeer-e-Tashreeq’.
Eminent jurispudents have stated that the origin of the ‘Takbeer-e-Tasreeq’ is when the Prophet Ibrahim made Hazrat Ismail lie down, Allah ordered Hazrat Jibraeel to take along a ‘fidyah’(ransom) and when Hazrat Jibraeel arrived there, he feared that Hazrat Ibrahim would slaughter Ismail and so he began shouting “Allah Akbar, Allah Akbar.”
Hearing his voice, Prophet Ibrahim took it as a glad tiding and exclaimed, “Laa ilaaha allallahu wallahu akbar.”
Hazrat Ismail also came to know that the ‘fidyah’ arrived and he got up saying, “Allahu akbar wa lillahil hamd,” and began to eulogise and thank Allah.