# The hand of Yahweh had been on me

"Yahweh was controlling me". See Ezekiel 1:3. 

# my mouth was opened

"Yahweh enabled me to speak". See how you translated "I will open your mouth" in Ezekiel 3:27.

# dawn

The time early in the morning when the light of the sun first appears.

# I was no longer mute

"I was no longer forced to be silent" or "I was no longer unable to speak". Ezekiel had been unable to speak anything except prophetic words since Ezekiel 3:26.