Does informing someone that you are praying for them in the unseen, or answering "yes" when asked, "Will you pray for me?" with a request for reciprocity, diminish the reward of the prayer?

The Shari'ah encourages a Muslim to supplicate for his brother in his absence, and there is a great reward for the supplicant, as the angel says, "And to you the like."

If the supplicant informs the one supplicated for about his supplication, there are two scenarios:

First: If he intends to boast or show favor, it is like boasting about charity, which nullifies the reward. However, the effect comes after the completion of the act of worship.

Second: If he intends to bring joy to his brother's heart, or to show affection and love, or if his informing is a response to a question, then this does not nullify the reward of the supplication. Rather, it is a righteous deed for which its doer is rewarded.

However, he should not ask his brother to supplicate for him in return, for this is seeking recompense for a righteous deed.