إِلَّا عِبَادَكَ مِنْهُمُ ٱلْمُخْلَصِينَ
Illaa 'ibaadaka minhumul mukhlaseen
all except Your devoted servants.’
except your servants among them, the sincere ones.
The limit comes from Iblis's own mouth, conceded before anyone imposes it on him, and God restates the same limit from the other side two verses later. The word for these servants has been read both ways: those whom God has made sincere, and those who make themselves so. One reading makes the protection a gift, the other an attainment, and the passage leaves the question open.