(a) It is narrated from Nafi' (may Allah have mercy on him) that Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) would perform ablution in hot weather and pass his hands over his armpits, and that did not break his ablution.
(b) Yahya bin Sa'id al-Ansari, Yazid bin Abi Habib, al-Layth bin Sa'd and Malik bin Anas (may Allah have mercy on them) said: There is no ablution for touching the armpits; Ibn Wahb (may Allah have mercy on him) reported this.
(c) The Shaykh (may Allah have mercy on him) said: This is the view of Imam al-Hasan al-Basri (may Allah have mercy on him) and al-Harith al-Ukli (may Allah have mercy on him), of the Successors (Tabi'in). This is also the position of Imam al-Shafi'i (may Allah have mercy on him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 658