What is the ruling on upbringing through bartering in religious matters, such as saying: "If you pray, I will give you a gift"? And can one benefit from the story of Ibn Umar's freeing of his slaves if they prayed, and his saying: "Whoever deceives us concerning Allah, we will be deceived by him"?

There is no harm in encouraging children and giving them prizes and gifts to motivate them to perform acts of obedience and devotion, while guiding them to seek reward from Allah and teaching them sincerity. Similarly, one may bargain allowing them to play in exchange for completing what is required of them. As for the story of Ibn Umar, its context is different; he used to emancipate slaves whom he admired, seeking nearness to Allah, based on His saying: "You will not attain righteousness until you spend from that which you love."