How can I replace a set of ENV commands in Dockerfiles with placing them to some other file, which can be reused?

I have two Dockerfiles (maybe will have more) with the list of environment variables, same for the both files. Let’s say:

ENV VAR1="value1"
ENV VAR2="value2"
ENV VAR3="value3"

Can I somehow move this setup to a file, which can be used in all the Dockerfiles, where it’s required?
I want to remove duplicates and have a common place for setting those variables.

Source: Docker Questions