Fighting the enemy: at what hour is it recommended?

Abu Hayyan (may Allah have mercy on him) said that a shaykh of Madinah stated: There was friendship and acquaintance between me and the scribe of Ubaydullah. I wrote to him asking him to write out for me the letter of Sayyiduna Abdullah bin Abi Awfa (may Allah be pleased with him) in which he said that the Messenger of Allah (peace and blessings be upon him) said: "Do not ask to meet the enemy. And when you meet the enemy, be steadfast, and know that Paradise is beneath the shade of the swords." And he (peace and blessings be upon him) would wait; when the sun had passed its zenith, he (peace and blessings be upon him) would attack the enemy.

Sayyiduna al-Nu'man bin Muqarrin (may Allah be pleased with him) said: I was present with the Messenger of Allah (peace and blessings be upon him) in battle. He (peace and blessings be upon him) did not fight in the early part of the day, and he (peace and blessings be upon him) delayed the fighting until the sun had passed its zenith, the winds were blowing, and help was descending.