(Al-Kahf) 18 : 81
فَأَرَدْنَا أَنْ يُبْدِلَهُمَا رَبُّهُمَا خَيْرًا مِنْهُ زَكَاةً وَأَقْرَبَ رُحْمًا
So We intended that their Lord should substitute for them one better than him in purity and nearer to them in mercy.
The Impartial Lord has given man the freedom either to be grateful or ungrateful vide verse 76: 3. So the believer who testifies Adhikr will not force anyone to become a believer. The duty of Messenger and believer is just to convey the Message Adhikr to whole mankind as explained in verses 5: 67 and 13: 40. Messenger and believer can’t implement anything which is against the dos and don’ts of Adhikr. So here Impartial Lord is directly doing a thing through His Angel Khidr. See explanation 11: 59; 13: 11 and 19-24.