"The Messenger of Allah commanded me (with Tathwib) in the Adhan for Fajr, and he forbade me to do so in the Adhan for 'Isha'." (Using translation from Ibn Mājah 715)
«أَمَرَنِي رَسُولُ اللهِ ﷺ أَنْ أُثَوِّبَ فِي الْفَجْرِ وَنَهَانِي أَنْ أُثَوِّبَ فِي الْعِشَاءِ»