It is narrated from Sayyidah Aishah (may Allah be pleased with her) that a Bedouin came to the Prophet (peace and blessings be upon him) and said: You kiss children? We do not kiss them. He (peace and blessings be upon him) said: "If Allah has removed mercy from your heart, what can I do about it?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 13577