Embracing Islam
Hadhrat Umar (May Allah be well pleased with him) embraced Islam 3 days after Hadhrat Ameer Hamzah embraced Islam in 6th year of Prophethood (6 Nabawi). Then his age was 27 years. (Tarikh Ul Khulafa, Vol. 1, Pg. No. 43; Al Kamil Fi Asmair Rijaal)
There is a Hadith in Jame’ Tirmidhi:
Translation: It is narrated on the authority of Hadhrat ‘Abdullah Bin ‘Umar that the Holy Prophet (Sallallahu alaihi wa sallam) prayed: O Allah! You grant dominance to Islam through either Abu Jahl or Umar Bin Khattab, whomever You love more. (Jame’ Tirmidhi, Hadith No. 4045)
In Sunan Ibn Majah, it is mentioned that the Holy Prophet (Sallallahu alaihi wa sallam) prayed specially for Hadhrat ‘Umar (May Allah be well pleased with him):
Translation: It is narrated on the authority of Hadhrat ‘Aisha Siddiqua (May Allah be well pleased with her), she said that the Holy Prophet (Sallallahu alaihi wa sallam) prayed: O Allah! You grant dominance to Islam by guiding ‘Umar to Islam. (Sunan Ibn Majah, Hadith No. 110)