Al-Kahf 70

قَالَ فَإِنِ ٱتَّبَعْتَنِى فَلَا تَسْـَٔلْنِى عَن شَىْءٍ حَتَّىٰٓ أُحْدِثَ لَكَ مِنْهُ ذِكْرًا ﴿٧٠﴾

Qala faini ittabaAAtanee fala tasalnee AAan shayin hatta ohditha laka minhu thikran

He (Khidr) said: "Then, if you follow me, ask me not about anything till I myself mention it to you." The Noble Quran