Hazrat Nafi’ narrates that when Hazrat Ibn Umar (may Allah be pleased with them) would say“Yarhamukallah”to someone who sneezed, the person would reply:“Yarhamuna Allahu wa iyyakum.”And when he himself sneezed and someone said“Yarhamukallah”to him as a supplication, he would say:“Yaghfirullahu lana wa lakum wa yarhamuna wa iyyakum.”