بُلُوغُ الْمَرَامِ
Bulugh al-Maram 1137
Marriage
وَعَنْ زِيَادِ اَلسَّهْمِيِّ - رضى الله عنه - قَالَ: { نَهَى رَسُولُ اَللَّهِ - صلى الله عليه وسلم -أَنْ تُسْتَرْضَعَ اَلْحَمْقَى. } أَخْرَجَهُ أَبُو دَاوُدَ وَهُوَ مُرْسَلٌ, وَلَيْسَتْ لِزِيَادٍ صُحْبَةٌ [1] .
Narrated Ziyad as-Sahmi: Allah's Messenger (ﷺ) forbade that a stupid woman may be asked to suckle an infant. [Abu Dawud reported it. It is Mursal (missing link after the Tabi'i) and Ziyad is not a Sahabi].
Sunnah.com reference: Book 8, Hadith 201