Sahih Muslim 544
Sahih Muslim · Book 5: The Book of Mosques and Places of Prayer · The permissibility of taking one or two steps while praying, and that is not disliked if done for a reason. The permissibility of the Imam praying in a place that is higher than the people praying behind him, if that is done for a reason, such as teaching them how to offer prayers, and other than that.
Abu Hazim reported:
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ ، حَدَّثَنَا يَعْقُوبُ بْنُ عَبْدِ الرَّحْمَنِ بْنِ مُحَمَّدِ بْنِ عَبْدِ اللَّهِ بْنِ عَبْدٍ الْقَارِيُّ الْقُرَشِيُّ ، حَدَّثَنِي أَبُو حَازِمٍ ، أَنَّ رِجَالاً، أَتَوْا سَهْلَ بْنَ سَعْدٍ ح قَالَ وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ ، وَزُهَيْرُ بْنُ حَرْبٍ ، وَابْنُ أَبِي عُمَرَ ، قَالُوا حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ ، عَنْ أَبِي حَازِمٍ ، قَالَ أَتَوْا سَهْلَ بْنَ سَعْدٍ فَسَأَلُوهُ مِنْ أَىِّ شَىْءٍ مِنْبَرُ النَّبِيِّ صلى الله عليه وسلم وَسَاقُوا الْحَدِيثَ نَحْوَ حَدِيثِ ابْنِ أَبِي حَازِمٍ .
They (the people) came to Sahl b. Sa'd and they asked him of what thing the pulpit of the Messenger of Allah (ﷺ) was made, and the rest of the hadith is the same.