Praise be to Allah.
Masturbation between husband and wife is not haram, rather, it is permissible. This is because it is a part of the enjoyment which Allah has allowed. Allah says (interpretation of the meaning):
"Those who guard their chastity (.e., [private parts, from illegal sexual acts) Except from their wives or (the captives and slaves) that their right hands possess, - for them, they are free from blame." [al-Muminun 23:5-6]
For more about masturbation, please see these answers: 329 , 99756 , 50017 , 2571 , 14587 , 23432 , and 83140 .
And Allah knows best.