in (one's) prayers
A phrase often used to express one's sympathy for someone else, especially someone who has just suffered a tragic loss or is otherwise experiencing a painful or challenging time. I'm so sorry to hear about your mom, Ellen. You're in my prayers. A: "I can't believe the Millers' house burned down." B: "I know, it's horrible. They're in all of our prayers."
in someone's prayers
[of someone] remembered and called by name when someone prays. I am sorry to hear of your sickness. You will be in our prayers. The whole family is in my prayers because they have suffered so much.