Send Salat on the Prophet ﷺ for Forgiveness (Hadith)

Ubayy ibn ka'b (RA) said: "I said: 'O Messenger of Allah! Indeed I say very much Salat for you. How much of my Salat should I make for you?' He (ﷺ) said: 'As you wish.'" [He said:] "I said: 'A fourth?' He (ﷺ) said: 'As you wish. But if you add more it would be better for you.' I said: 'Then half?' He (ﷺ) said: 'As you wish. And if you add more it would be better [for you].'" [He said:] "I said: 'Then two-thirds? 'He (ﷺ) said: 'As you wish, but if you add more it would be better for you.' I said: 'Should I make all of my Salat for you?' He (ﷺ) said: 'Then your problems would be solved and your sins would be forgiven.'