'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. Sheikh Salim Al-Hilali in his book "Bahjatun-Nazireen, Sharh Riyad-us- Saliheen" classifies it as "Da'if", the reason being that 'Asim bin 'Abdullah is "weak" in narration].

وعن عمر بن الخطاب رضي الله عنه قال: استأذنت النبي ﷺ في العمرة، فأذن لي، وقال: "لا تنسنا يا أخي من دعائك" فقال كلمة ما يسرني أن لي بها الدنيا.
وفي رواية قال: "أشركنا يا أخي في دعائك".
حديث صحيح ((رواه أبو داود، والترمذي وقال: حديث حسن صحيح)).