question #2 Sahih al-Bukhari 2547, Book 49, Hadith 30 : How does observing the rights of Allah and one’s master lead to a double reward for a slave?

The Prophet (ﷺ) said, “He who has a slave-girl and teaches her good manners and improves her education
and then manumits and marries her, will get a double reward; and any slave who observes Allah’s
right and his master’s right will get a double reward.”