The Prophet ﷺ said: One should not take a false oath at this pulpit of mine even on a green tooth-stick; otherwise he will make his abode in Hell, or Hell will be certain for him. (Using translation from Abū Dāʾūd 3246)
قَالَ رَسُولُ اللهِ ﷺ لَا يَحْلِفُ رَجُلٌ عَلَى يَمِينٍ آثِمَةٍ عِنْدَ هَذَا الْمِنْبَرِ إِلَّا تَبَوَّأَ مَقْعَدَهُ مِنَ النَّارِ وَلَوْ عَلَى سِوَاكٍ أَخْضَرَ