Arabic text
عن أنس رضي الله عنه قَالَ: لَمَّا جَاءَ أهْلُ اليَمَنِ، قَالَ رسولُ الله صلى الله عليه وسلم : "قَدْ جَاءكُمْ أهْلُ اليَمَنِ" وَهُمْ أوَّلُ مَنْ جَاءَ بِالمُصَافَحَة.
Translation
Anas (may Allah be pleased with him) reported: When the people of Yemen came, the Messenger of Allah (may Allah’s peace and blessings be upon him) said: "There have come to you the people of Yemen." They were the first to bring the (practice of) handshake.
Explanation
The Prophet (may Allah's peace and blessings be upon him) said: "There have come to you the people of Yemen,” he meant by this the Ash‘ariyyūn, who were the people of Abu Mūsa al-Ash‘ari (may Allah be pleased with them). This is supported by the Hadīth narrated by Ahmad in his Musnad (3/155) on the authority of Anas ibn Mālik who reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "Tomorrow a people will come to you whose hearts are softer for Islam than yours." Anas said: "The Ash‘ariyyūn came, and among them was Abu Mūsa al-Ash‘ari. When they approached Madīnah, they began chanting lines of poetry that meant: 'Tomorrow we will meet our beloved ones, Muhammad and his group.' When they arrived, they began shaking hands. So, they were the first to introduce the handshake.”
Source: HadeethEnc.com