"And the disbeliever has ever been, against his Lord, an assistant [to Satan]," meaning: a supporter. He says: He assists Satan in abandoning the command of his Lord.
Surat al-Furqan, from (verse 56 to verse 62).
﴿وَكَانَ الْكَافِرُ عَلَى رَبِّهِ ظَهِيرًا﴾ أَيْ: عَوِينًا؛ يَقُولُ: يُظَاهِرُ الشَّيْطَانَ على ترك أَمر ربه.
سُورَة الْفرْقَان من (آيَة ٥٦ آيَة ٦٢).