Some Scholars were asked if Khidr is still alive, and they replied with the verse: "And We did not grant immortality to any human before you." - Ibn al-Qayyim

Al-Manar al-Munif Ibn al-Qayyim cover
Some scholars were asked if Khidr is alive - Ibn al-Qayyim part 1
Some scholars were asked if Khidr is alive - Ibn al-Qayyim part 2
Some scholars were asked if Khidr is alive - Ibn al-Qayyim part 3
Some scholars were asked if Khidr is alive - Ibn al-Qayyim part 4