The Night Before
Hanzala ibn Abi Amir had married Jamila bint Ubayy ibn Salul — a daughter of the leader of the munafiqun of Medina, now married to a sincere Companion — on the night before Uhud. He consummated the marriage and therefore entered the state of ritual impurity (janaba) that required the major ritual bath (ghusl) before he could pray.
The call came at dawn. He went.
The Angels’ Report
After Uhud, the Prophet told his Companions: “I saw the angels washing Hanzala between heaven and earth with water from silver vessels.” He then asked his wife what had happened. She confirmed that he had left before performing his ghusl.
The narration: Hanzala left the marriage bed, went directly to the battlefield, fought, and was killed — still in the state of janaba. The angels performed what he had not had time to perform.
His Father’s Opposition
A poignant biographical note: Hanzala’s father, Abi Amir al-Rahib (the Monk), was among the most persistent opponents of the Prophet in Medina — a man who had expected to lead Medina’s spiritual life and found himself superseded. Abi Amir eventually went to fight on the Meccan side. Father and son were, at Uhud, on opposite sides of the battlefield.
See also: Seerah Sad Ibn Muadh, Seerah Qatada Ibn Al Numan, Seerah Usama Ibn Zayd, Seerah Julaybib, Seerah Uhud