A younger companion
Abdullah accepted Islam while young and migrated to Madinah. His father was Umar ibn al-Khattab and his sister was Hafsa bint Umar, which brought him into close contact with Muhammad’s ﷺ household.
Source: ABDULLAH b. ÖMER b. HATTÂB — TDV İslâm Ansiklopedisi
Restraint in public conflict
During the civil conflicts after Uthman’s death, Abdullah generally avoided fighting and declined leadership claims. His long life made him an important point of reference for later generations seeking knowledge of the earliest community.
Source: ABDULLAH b. ÖMER b. HATTÂB — TDV İslâm Ansiklopedisi