Source: The Great Interpretation of Dreams (Ibn Sirin)
A handshake in a dream indicates reconciliation, affection, and a pact. Shaking hands with an enemy indicates reconciliation with him.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
A handshake indicates an oath of allegiance or a partnership. Whoever sees himself shaking hands with a man is partnering with him in a matter.
Source: Signs in the Science of Expressions (Ibn Shaheen)
A handshake is interpreted as goodness and benefit. Whoever sees himself shaking hands with someone will receive good from him.