wget http://ftp.de.debian.org/debian/dists/jessie/main/binary-amd64/Packages.gz -O jessie.main.binary-amd64.Packages.gz
wget http://ftp.de.debian.org/debian/dists/jessie/non-free/binary-amd64/Packages.gz -O jessie.non-free.binary-amd64.Packages.gz
gunzip jessie.main.binary-amd64.Packages.gz jessie.non-free.binary-amd64.Packages.gz
This will give you two files called
jessie.non-free.binary-amd64.Packages, which will jointly contain a list of packages corresponding to the source line
deb http://ftp.de.debian.org/debian jessie main non-free
As Stephen noted, if the sources entry is in your
sources.list, then these files, along with many others, will be automatically downloaded to your disk, along with many others.