1
general::
An unexpected aid, advantage, or assistance, as in After all the criticism in the media, that favorable evaluation was like manna from heaven. This expression alludes to the food (manna) that miraculously appears to feed the Israelites on their journey from Egypt to the Promised Land (Exodus 16:15).
American Heritage Idioms
2
general::
Phrase(s): manna from heaven
Fig. unexpected help or comfort. (A biblical reference.) • The arrival of the rescue team was like manna from heaven to the injured climber. • The offer of a new job just as she had been fired was manna from heaven to Joan.
McGrawhill's American Idioms And Phrasal Verbs