(a) Salim (may Allah have mercy on him) narrates from his father that a man's kissing his wife and touching her body with his hand are part of mulamasah (touching), and whoever kisses his wife or touches her with his hand must perform ablution.
(b) In the narration of Ibn Bukayr the wording is: ablution becomes obligatory upon him.
(c) This is the view of Sayyiduna Umar, Sayyiduna Abdullah bin Mas'ud and Sayyiduna Abdullah bin Umar (may Allah be pleased with them). Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) differed from them: he interpreted the mulamasah mentioned in the Book of Allah as intercourse, and he did not hold that kissing requires ablution.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 608