Source: The Great Interpretation of Dreams (Ibn Sirin)
(By analogy with a knife and sword) A dagger in a dream indicates a male child, a strong argument, or a loyal friend. Stabbing with it indicates hurtful words.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
(By analogy) A dagger indicates strength and power. Whoever sees himself carrying one will gain strength.
Source: Signs in the Science of Expressions (Ibn Shaheen)
(By analogy) A dagger is interpreted as goodness and strength. Whoever sees himself stabbing an enemy with it will triumph over him.