BismAllah Ar-Rehman Ar-Raheem
"I had no knowledge of the Highest Chiefs when they disputed; It is revealed unto me only that I may be a plain warner." Verse 38:69-70 (Surah Sad).
It's very important to clearly know what the expression "Highest Chiefs" refers to. In various other translations this expression varies a little such as "exalted chiefs," "chiefs" or "High Council."
Verses 38:69-70 allude to the dispute between Allah Almighty and Satan, when Satan refused to obey the command of The Almighty to prostrate before Adam who was the first human being created by HIM. As we know, this incident is narrated in several Surahs of the Noble Quran. It's mentioned in Surah Sad in the Verses that follow the above two Verses 69 and 70. It's also mentioned in Surah Al-Baqra 30-39, Surah Al-Araf 11-25, Surah Al-Hijr 26-44, Surah Bani Isra'il 61-65, Surah Al-Kahf: 50 and Surah Ta Ha: 116-126.
As rightly understood and explained by all exegesists, the dialogue in this incident between Allah Almighty and Satan was not direct, that is, Allah did not speak directly to Satan. Rather, the dialogue took place through the angels. The above Verses are a clear evidence of that. Allah appointed some of the angels to confront Satan with the Divine Words and to tell him that Allah affirmed him an outcast forever because of his disobedience, refusing to prostrate before Adam as commanded by HIM. In other words, the angels were the messengers of Allah Almighty, confronting Satan for his disobedience with the Message of Allah as directed by Him. Hence the expression "Highest Chiefs" refers to the participants of this argument, that is, the angels against Satan.
Please know, the expression "Highest Chiefs" does NOT include Allah Almighty. The name of Allah always comes alone. He can NEVER be included with anyone else. He is The Almighty, the Sole Creator, and HE is far above all His creations. "Highest Chiefs" mean the creations of Allah Almighty or the angels who were arguing in this dispute. All angels and jinn (which includes Satan) are the slaves of Allah and created by HIM.
In Muhammad Sarwar's translation, it's directly mentioned "angels" quoted as follows: "I have no knowledge of the dispute among the angels (concerning their attitude towards Adam)." 38:69.
Corpus Quran (word by word translation) mentions it as "Not is for me any knowledge (of) the chiefs, the exalted when they were disputing." (38:69).