I am downloading the Debian source files for the heimdal package by running this commandapt-get source --download-only heimdalThis downloads the source files for the release sid (unstable). However, what I want are the sources for release stretch (stable). I am running this command on a Debian jessie (oldstable) machine. I tried adding the -t stable option but that still gave me the source files for unstable.How do I do this? 
Download Debian source files for stable rather than unstable
debian;apt
apt-get source downloads the newest source it has available by default, but you can override that by specifying a version any of the normal ways:apt-get source --download-only heimdal=7.1.0+dfsg-13+deb9u1apt-get source --download-only heimdal/stretchshould both work, provided you also have stretch deb-src lines in your sources.list.Another alternative, depending on your workflow, is dgit:dgit clone heimdal stretch,-securitywill leave you with a git repository in heimdal/