Mishkat al-Masabih 4572
Abu Kabsha al-Anmari told that God’s messenger had himself cupped on the top of his head because of the poisoned sheep.* Ma'mar said:
I had myself cupped like that in the middle of my head for a reason other than poison and suffered some loss of memory till I was recommended to use Fatihat al-Kitab in the prayer. 

Razin transmitted it.

* An attempt was made to poison the Prophet after the conquest of Khaibar in 7 A.H., but when he had taken a mouthful of the poisoned meat he spat it out realizing that it was poisoned.
وَعَن أبي كَبْشَة الْأَنْمَارِيِّ: أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ احْتَجَمَ عَلَى هَامَتِهِ مِنَ الشَّاةِ الْمَسْمُومَةِ قَالَ مَعْمَرٌ: فَاحْتَجَمْتُ أَنَا مِنْ غَيْرِ سُمٍّ كَذَلِكَ فِي يَافُوخِي فَذَهَبَ حُسْنُ الْحِفْظِ عَنِّي حَتَّى كُنْتُ أُلَقَّنُ فَاتِحَةَ الْكِتَابِ فِي الصَّلَاةِ. رَوَاهُ رزين