Tradition

The Prophet (s.a.w.a.) informed (about Fatima Zahra (s.a.)): …Allah has appointed a cavalry of angels to protect Fatima from all sides: her front, her back, her right side, and her left side. They will accompany her throughout her life. After she dies, they will be next to her grave and they will continuously convey her salutations and to her father (s.a.w.a.), her husband (a.s.) and her two sons (a.s.). Those who visit me after my death are just like those who visit me when I am alive, and those who visit Fatima (s.a.) are like those who visit me. Those who visit Ali ibne Abi Talib (a.s.) are like those visit Fatima (s.a.). Those who visit Hasan (a.s.) and Husain (a.s.) are like those who visit Ali ibne Abi Talib (a.s.). Those who visit their sons (a.s.) are like those who visit Hasan (a.s.) and Husain (a.s.).
Bashaarah al-Mustafa Le Shiah al-Murtaza v 2 p 139