I say, and with God's success: Visiting graves in general is a Sunnah every week, and the graves of the saints, the righteous, and the prophets are most deserving of this; due to the spiritual benefit and the lessons and admonitions it provides. However, there is a suspicion regarding slaughtering at these graves that it may be for the graves, even if it is actually for God Almighty; therefore, it is preferable to avoid it, and slaughtering in all places is the same, as long as the intention is sincere for God Almighty, and God knows best.