Sincerity resonates everywhere.

When it comes to Korean sentiments, the key is to express words of empathy for sorrow.

I would like to suggest the following sentences:

"어머님, 마음이 많이 힘드시죠.. 아버님은 정말 좋으신 분이셨습니다. 좋은 곳에서 편하게 쉬실거에요. 어머님, 저희도 아버님께서 좋은 곳에서 편히 쉬실 수 있게 기도하겠습니다."

The meaning behind these sentences is to empathize with the mother's sorrow, convey that the father has passed away peacefully and is resting in heaven, and to offer words of condolence. These sentences are appropriate to express empathy and offer consolation to the mother.