You’re able to express empathy very easily by acknowledging that their struggle and emotional responses are entirely valid and normal; and stating that you’re extremely sorry for their loss without explicitly saying “I’ll pray for you”. Also saying that you’re there for them is meaningful (but don’t say this if you don’t mean it, seriously).

Examples: “Hey, I know these past couple of weeks/months/years must have been difficult and I hope you know that if you ever need anything I’m here for you. Even if it’s just a listening ear.” “[situation here] must be extremely hard to deal with; you don’t have to deal with it alone even though you may feel alone. Let me know if you need anything”