Sunan an Nasai
5563
Sahih Isnaad+2

It was narrated that Anas bin Malik said:"The Messenger of Allah [SAW] forbade us to soak two things together when one is more potent than the other. I asked him about Fadikh (a drink made from fresh dates cut open) and he forbade it. He disliked the extra bit on Al-Busr, fearing that that might make it two things, so we used to cut it off

Sahih IsnaadAbu Ghuddah
Sahih IsnaadAl-Albani