I heard the Messenger of Allah ﷺ say: Were it not that it would be too difficult for my ummah, I would have commanded them to use the siwak every time of prayer, and I would have delayed Ishaʿ until the first third of the night had passed, because when the first third of the night has passed. Allah may he be exalted descends to the first heaven and stays there until dawn comes, and says: Is there any asking so that he might be given? Is there anyone praying so that he might be answered? Is there any sick person asking for healing so that he might be healed? Is there any sinner asking for forgiveness, so that he might be forgiven? A hadeeth like that of Abu Hurairah was narrated from ʿAli bin Abi Talib ؓ from the Prophet ﷺ Abi Talib.
سَمِعْتُ رَسُولَ اللهِ ﷺ يَقُولُ لَوْلا أَنْ أَشُقَّ عَلَى أُمَّتِي لَأَمَرْتُهُمْ بِالسِّوَاكِ عِنْدَ كُلِّ صَلاةٍ وَلَأَخَّرْتُ عِشَاءَ الْآخِرَةِ إِلَى ثُلُثِ اللَّيْلِ الْأَوَّلِ فَإِنَّهُ إِذَا مَضَى ثُلُثُ اللَّيْلِ الْأَوَّلُ هَبَطَ اللهُ تَعَالَى إِلَى السَّمَاءِ الدُّنْيَا فَلَمْ يَزَلْ هُنَاكَ حَتَّى يَطْلُعَ الْفَجْرُ فَيَقُولَ قَائِلٌ أَلا سَائِلٌ يُعْطَى أَلا دَاعٍ يُجَابُ أَلا سَقِيمٌ يَسْتَشْفِي فَيُشْفَى أَلا مُذْنِبٌ يَسْتَغْفِرُ فَيُغْفَرَ لَهُ؟