let go of

16. PHRASE : let inflects, oft PHR of n

If you let go of someone or something, you stop holding them.

• She let go of Mona's hand and took a sip of her drink.     ..... Cobuild
  
• The little boy let go of the string and his balloon drifted high above the trees. 
• He was holding onto the hand of his boss's wife, and even when his boss walked in he didn't let go.       .... Cambridge-Am-Idioms