Friday night's dream,
On the Saturday told,
Is sure to come true,
Be it never so old.
Here's a slightly different version from The Little Mother Goose (1912), illustrated by Jessie Willcox Smith:
Friday night's dream, on Saturday told,
Is sure to come true, be it ever so old.
Thanks and Acknowledgements
This proverb can be found in The Nursery Rhyme Book, edited by Andrew Lang and illustrated by L. Leslie Brooke (1897).