Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
tabarani:16802al-Ḥusayn b. Isḥāq > Yūsuf b. Muḥammad b. Sābiq > Abū Yaḥyá al-Ḥimmānī > al-Aʿmash

[Machine] I heard Al-A'mash saying, "If you see Muawiyah, you would say, 'This is the Mahdi.'"  

الطبراني:١٦٨٠٢حَدَّثَنَا الْحُسَيْنُ بْنُ إِسْحَاقَ ثنا يُوسُفُ بْنُ مُحَمَّدِ بْنِ سَابِقٍ سَمِعْتُ أَبَا يَحْيَى الْحِمَّانِيَّ يَقُولُ

سَمِعْتُ الْأَعْمَشَ يَقُولُ لَوْ رَأَيْتُمْ مُعَاوِيَةَ لَقُلْتُمْ هَذَا الْمَهْدِيُّ