Note GREP_OPTIONS in man page.

man/pass.1

@@ -76,7 +76,8 @@ program. This command is alternatively named \fBlist\fP.
 Searches inside each decrypted password file for \fIsearch-string\fP, and displays line
 containing matched string along with filename. Uses
 .BR grep (1)
-for matching.
+for matching. Make use of the \fIGREP_OPTIONS\fP environment variable to set particular
+options.
 .TP
 \fBfind\fP \fIpass-names\fP...
 List names of passwords inside the tree that match \fIpass-names\fP by using the