Muawiya said (to the people), "You offer a prayer which we, who were the companions of the Prophet ﷺ never saw the Prophet ﷺ offering, and he forbade its offering," i.e. the two rakʿat after the compulsory ʿAsr prayer.
إِنَّكُمْ لَتُصَلُّونَ صَلاَةً لَقَدْ صَحِبْنَا النَّبِيَّ ﷺ فَمَا رَأَيْنَاهُ يُصَلِّيهَا وَلَقَدْ نَهَى عَنْهُمَا يَعْنِي الرَّكْعَتَيْنِ بَعْدَ الْعَصْرِ