Is it permissible to deliver a sermon after burying the deceased, or should one be limited to saying, "Ask for forgiveness for your brother and for him to be steadfast, for he is now being questioned"?

Admonition at the grave is permissible if it aligns with what is narrated in the Sunnah: the admonisher sits and does not deliver a sermon while standing, as the Prophet, peace be upon him, did. He admonished the Companions while they were sitting around him, and he spoke about the state of a person at the time of death and burial, or while he was standing at the grave, admonishing people without delivering a sermon. These matters should not be a cause for contention and dispute among Muslims, for the unity of hearts and harmony among believers is a great religious objective.