The Ornaments of Gold - 43:86
Those whom they call besides Him cannot intercede. Except those who knowingly bear witness to the truth
The intercession of the intercessors takes the form of their testimony to the truth presented:
Prophet Jonah/10:3
It is Allah, your Lord, Who created the heavens and the earth in six days and then established all authority. He directs every affair. No one can intercede without His permission. This is Allah your Lord, so serve Him. Do you not take heed?
Mary/19:85
We will gather the righteous in groups of guests before the Most Merciful,
Mary/19:87
None can intercede except those who have taken a promise with the Most Merciful.
Ta-Ha/20:108
On that Day they will obey the caller without the slightest deviation. The voices are muted in the presence of the Most Merciful; you will hear nothing but a whisper.
Ta-Ha/20:109
On that Day, the intercession of none will avail but he whom the Most Merciful permits and whose word He approves.
The Ornaments of Gold/43:86
Those whom they call besides Him cannot intercede. Except those who knowingly bear witness to the truth
The Prophets/21:26
"They said: "The Most Merciful has taken a child". He is exalted. But they are honorable servants."
The Prophets/21:27
They do not utter a word before Him, and they follow His commands strictly.
The Prophets/21:28
He knows their past and their future. They do not intercede for anyone except those whom He pleases. Even they tremble in reverence before Him.
The Star/53:26
Even the intercession of the angels in the heavens is of no avail. Only after Allah permits it for whom He wills and it is in accordance with His pleasure...
Sheva/34:23
"Intercession avails nothing in His sight except that which He permits. Finally, when their fear is removed from their hearts, they say, "What did your Lord say?"They will say, "He has told the truth". He is the Most High, the Greatest."