‘By Him who dominates my soul I swear That you are the Prophet of this nation … You will be abused and you will be Persecuted. If I should ever live to see ...

The statement mentioned in the question was made by Waraqah bin Nawfal. Waraqah bin Nawfal was the cousin of Khadijah bint Khuwaylid, the first wife of Prophet Muhammad (peace be upon him). He was a scholar of the scriptures and was well-versed in the knowledge of the previous Prophets. When the first revelation came to the Prophet Muhammad (peace be upon him), he was distressed and confused. It was Khadijah who took him to her cousin, Waraqah bin Nawfal, who reassured him that he was indeed a Prophet of Allah and that he would face persecution from his people. The statement mentioned above is from Waraqah bin Nawfal to the Prophet Muhammad (peace be upon him), expressing his belief in his prophethood and his commitment to help the cause of Allah.