Some packages from proposed-updates may also be made available via the stable-updates mechanism. This path will be used for updates which many users may wish to install on their systems before the next point release is made, such as updates to virus scanners and timezone data. All packages from stable-updates will be included in point releases.
deb http://httpredir.debian.org/debian stretch-updates main deb-src http://httpredir.debian.org/debian stretch-updates main
For Debian 8 "Jessie", jessie-updates no longer exists as this suite no longer receives updates since 2018-05-17.
The next time you run apt-get update, the system will become aware of the packages in the (old)stable-updates section and will consider them when looking for packages to upgrade.
Note that if APT::Default-Release is set in your /etc/apt/apt.conf (or in any of /etc/apt/apt.conf.d/*), then, in order for automatic upgrades to work, it is necessary to add a similar configuration block to /etc/apt/preferences (see apt_preferences(5) for more information):
Package: * Pin: release o=Debian,n=stretch-updates Pin-Priority: 990
When a new package is made available via (old)stable-updates, this will be announced on the debian-stable-announce mailing list.