The ESV reads, “I was told.” The Greek actually has, “They said to me.” The third person plural form “they” refers to the two parties who had spoken to John earlier in the chapter. Those two were the mighty angel of Revelation 10:1–3, Revelation 10:5–7, Revelation 10:9–10 and the heavenly voice of Revelation 10:4 and Revelation 10:8. These two now jointly give John a further instruction. The fact that they do so together indicates the unity of their respective actions and words throughout the chapter.
11 And I was told, “You must again prophesy about many peoples and nations and languages and kings.”