As we draw closer to the Sacred month of Dhul Hijjah, it becomes more relevant to explore the story of Ibrahim and his perfect monotheism, as well as the events from his life which help us see why he was declared as Khalilullah (Friend of Allah ﷻ).
The story of Ibrahim عليه السلام begins most notably with his declaration and expression of the oneness of Allah ﷻ.
Ibrahim عليه السلام questioned his uncle, Aazar, about his taking the idols that he (Aazar) carved from his own hands as God, when it can neither harm nor benefit, and it is a created thing.
Then we see the debate Ibrahim عليه السلام poses; to those who worship the stars which fade when morning comes, so how can one think the transitory is worthy of worship? Then what of the moon? The moon too becomes outshone by the sun during day. So what of the sun then, if not the moon? The sun too sets.
From this beautiful example we see how Ibrahim عليه السلام had resolute, firm and perfect monotheism, and that he was on a divine mission to establish truth and eradicate falsehood. And even in this, he did it in such a manner that the people around him would understand.

It is an astounding thing to see that people can worship what their own hands make, and worship that which neither responds to, or benefits, them — that which can be destroyed.
So when the people of his community were not present, he destroyed all the idols, except one. The largest one he left remaining. When the community brought him for questioning, he told them that it was the biggest of the idols that had done it, and to ask it, if they can speak.
They said “…You certainly know that they cannot speak” (Quran 21:65). Ibrahim عليه السلام responded to them by saying “Do you worship, instead of God, what can neither benefit you in anything, nor harm you?”; and due to this they sought to throw him into a large fire in retribution.
But Allah ﷻ, He who can help, the best of Helpers; He who responds “al-Mujib”, told the fire to be coolness and safety, and thereby the fire became pleasant and Allah ﷻ protected him and provided for Ibrahim عليه السلام. Thereby demonstrating the complete Truth of the worship of Allah ﷻ.