Hijrah (Migrating to Madinah Munawwarah):

Hazrat Abu Zar (radhiyallahu ‘anhu) migrated to Madinah Munawwarah after the battles of Badr and Uhud were fought. In some narrations, it is mentioned that he migrated after the battle of Khandaq.

(Isaabah 7/107, Usdul Ghaabah 1/343, ibn Sa‘d 4/170, Istee‘aab 1/321)

Rasulullah (sallallahu ‘alaihi wasallam) testifies to the truthfulness of Hazrat Abu Zar (radhiyallahu ‘anhu):

Hazrat ‘Abdullah bin ‘Amr (radhiyallahu ‘anhuma) narrates that he heard Rasulullah (sallallahu ‘alaihi wasallam) saying, “The sky has not shaded and the earth has not carried a person more truthful than Hazrat Abu Zar (radhiyallahu ‘anhu).” Note: While this hadith shows that Hazrat Abu Zar (radhiyallahu ‘anhu) had attained the highest level of truthfulness, it does not negate other Sahaabah (radhiyallahu ‘anhum), such as the Khulafaa-e-Raashideen, also having the highest level of truthfulness.

(Tirmizi #3801)