Kitāb al-Ghayba

Hadith 663
occultationyunus
399- وروي في خبر آخر: أن في صاحب الزمان عليه السلام شبها من يونس؛رجوعه من غيبته بشرخ الشباب.
H 399 - It is mentioned in another report that: There is a similarity between Prophet Yunus (a.s) and Imam Mahdi (a.s); and it is that he would return from his occultation as a young man.
Source: Shaykh Muḥammad b. al-Ḥasan al-Ṭūsī