Tafsir of Al-Anbiya' 21:51

The Story of Ibrahim and his People Allah tells:

ولقد آتينا إبراهيم رشده من قبل وكنا به عالمين

And indeed We bestowed aforetime on Ibrahim his guidance, Allah tells us about His close Friend Ibrahim, peace be upon him, and how He bestowed upon him guidance aforetime, i.e., from an early age He inspired him with truth and evidence against his people, as Allah says elsewhere:

وتلك حجتنا ءاتينها إبرهيم على قومه

And that was Our proof which We gave Ibrahim against his people. (6:83) The point here is that Allah is telling us that He gave guidance to Ibrahim aforetime, i.e., He had already guided him at an early age.

وكنا به عالمين

and We were Well-Acquainted with him. means, and he was worthy of that. Then Allah says:

إذ قال ﻻبيه وقومه ما هذه التماثيل التي أنتم لها عاكفون