Dhul-Kifl (peace be upon him) is mentioned in the Qur'an alongside Isma'il and Idris, all of whom were among the patient (21:85). Allah admitted them into His mercy, for they were among the righteous (21:86).
He is also named among Isma'il and Al-Yasa', all counted among the best of people, the chosen (38:48). Beyond these affirmations of his patience and righteousness, the Qur'an provides no detailed narrative of his life.
In keeping with authenticity, only what Allah has affirmed about him is retained: that he was patient, righteous, chosen, and among those admitted into Allah's mercy. Later stories that add detail to his life are unverified and are therefore omitted.