This is an “Ema”. “Ema” are small wooden plaques on which Shinto worshippers write their prayers or wishes. The ema are then left hanging up at the shrine, where the kami (spirits or gods) receive them. They bear various pictures, often of animals or other Shinto imagery, and many have the word gan’i (願意), meaning “wish”, written along the side. In ancient times people would donate horses to the shrines for good favor, over time this was transferred to a wooden plaque with a picture of a horse, and later still to the various wooden plaques sold today for the same purpose.

Ema are sold for various wishes. Common reasons for buying a plaque are for success in work or on exams, marital bliss, to have children, and health. Some shrines specialize in certain types of these plaques, and the larger shrines may offer more than one. Sales of ema help support the shrine financially.

********This Ema is from Yakushi-ji in Nara.
Yakushi-ji  is one of the most famous imperial and ancient Buddhist temples in Japan, that was once one of the Seven Great Temples of Nanto, located in Nara. The temple is the headquarters of the Hossō school of Japanese Buddhism. Yakushi-ji is one of the sites that are collectively inscribed as a UNESCO World Heritage Site, under the name of “Historic Monuments of Ancient Nara.”

The main object of veneration, Yakushi Nyorai, also named “The Medicine Buddha”, was one of the first Buddhist Deities to arrive in Japan from China in 680, and gives the temple its name.

On the Ema:
心　kokoro = heart

南都　=　nanto = literally “the seven great temples of Nanto (synonym of Nara)”, is a historical common name generally referring to the powerful and influential seven Buddhist temples located in Nara.

薬師寺　＝　yakushi-ji temple

奉納　＝　hounou = dedication

This Ema is from  十月二日　=　Oct 2nd (not sure of the year).
It measures about 13cm x 9cm x 7mm. 

https://www.etsy.com/listing/514168386/japanese-fabric-cotton-fabric-1-yard-red?ref=shop_home_active_18