[Machine] The Messenger of Allah ﷺ said, "If it were not difficult for my Ummah, I would have commanded them to delay the Isha prayer and use the siwak (toothstick) before every prayer." Abu Sa'id added in his narration: Al-Shafi'i said, "This is evidence that using the siwak is not obligatory, but rather a choice. Because if it were obligatory, he would have either commanded them to do it or not to do it."  

أَنَّ رَسُولَ اللهِ ﷺ قَالَ لَوْلَا أَنْ أَشُقَّ عَلَى أُمَّتِي لَأَمَرْتُهُمْ بِتَأْخِيرِ الْعِشَاءِ وَالسِّوَاكِ عِنْدَ كُلِّ صَلَاةٍ زَادَ أَبُو سَعِيدٍ فِي رِوَايَتِهِ قَالَ الشَّافِعِيُّ وَفِي هَذَا دَلِيلٌ عَلَى أَنَّ السِّوَاكَ لَيْسَ بِوَاجِبٍ وَأَنَّهُ اخْتِيَارٌ لِأَنَّهُ لَوْ كَانَ وَاجِبًا أَمَرَهُمْ بِهِ شَقَّ أَوْ لَمْ يَشُقَّ