Scholars differ whether Takbir at-Tashreeq is compulsory or highly encouraged, there is also disagreement over the wording to be used.
[3][4] Ibrahim was ordered by Allah to sacrifice what is most beloved to him, his only son Ismail.
So he prepared his own heart to sacrifice Ismail and told him of this.
The son readily agreed to submit to Allah's wish.
‘Ibrahim heard the voice of the angels and said: "La 'ilaha 'ill-allahu wa Allahu Akbar" (There is none worthy of worship besides Allah and Allah is the Greatest).