{And this is the promise} (kai haut(8820)estin h(8820)epaggelia).
See  1:5  for the same idiom with aggelia (message). This is
the only instance of epaggelia in the Johannine writings. Here
"the promise" is explained to be "the life eternal" ( 1:2 ). In
 Ac 1:4  the word is used for the coming of the Holy Spirit. {He
promised} (autos ep(8867)geilato). First aorist middle indicative
of epaggell(935c). Autos (he) is Christ as is seen in  3:3  by
ekeinos.