Riyad as-Salihin

'Umar bin Al-Khattab (May Allah be pleased with him) reported: I sought permission of the Prophet (ﷺ) to perform 'Umrah. He granted me leave and said, "Dear brother! Do not forget us in your supplications". ('Umar added): This is something I would not exchange for the whole world.

Another narration is: He (ﷺ) said, "Include us, my dear brother, in your supplications." [Abu Dawud and At-Tirmidhi, who categorized the Hadith as Hasan Sahih.].