Abdullah Ibn Umar reports: “When we returned home after the siege by the confederate tribes was ended, the Prophet (peace be upon him) ordered us: 'No one should offer the Asr prayer except at the Qurayzah quarters. Some of us were still on the way when Asr was due. Some said that they would not pray until they have arrived at Qurayzah, while others said that they would pray on the way, because the Prophet did not wish anyone to delay prayers until its time was over. The Prophet was told of this, and he did not reproach either group.” (Related by Al-Bukhari)
The siege referred to in this Hadith was when the combined forces of major Arabian tribes, together with their Jewish allies, besieged Madinah, with the declared aim of exterminating Islam and all Muslims. The Prophet and his companions dug a moat along the area where these forces could come into Madinah, which was wide and deep enough to prevent any breach of their lines. The Muslims were able to hold on indefinitely because their enemy could not force entry, no matter how much they tried. It was only after the Jewish tribe of Qurayzah, which was bound by a treaty of friendship and alliance with the Muslims, decided to switch sides and attack the Muslims from behind that the Muslims were in real danger. Still, the Muslims were determined to continue with their resistance. Ultimately, the Muslims were able to create doubts among the various parties of their enemies, which led to the withdrawal of the Arabian tribes, humiliated and defeated without even putting up a fight. The Muslims were then able to go to their homes to rest.
However, on orders from God, the Prophet sent out callers requiring all Muslims to move against the traitors of Qurayzah. The order was in the terms set out in the quoted Hadith: 'No one should offer the Asr prayer except at the Qurayzah quarters.' The Prophet's companions immediately complied with the Prophet's order, as they always did. They set out in small groups, heading out to Qurayzah's forts where they would join the Prophet.
As they marched on, quite a long distance that took more than a couple of hours, it was time for Asr prayer. They feared that by the time they would reach their destination they would have missed their prayer, as the sun would have set. Some of them argued that the Prophet did not wish them to miss their prayer; rather, he only indicated the urgency of setting out. Therefore, they stopped to pray on the way, before they resumed their march. Others took the order quite literally. They argued that the occasion was special and, therefore, the Prophet wanted them to get to the Qurayzah quarter so that they would pray there. Hence, they did not stop. Although they arrived after sunset, which meant that the time range for Asr had passed, they prayed it on arrival.
The reporter of the Hadith makes it clear that the Prophet did not take an issue with either group. He accepted both as correct. This is an indication that some situations admit more than one acceptable alternative. If one exercises one's discretion to arrive at the right choice, God will accept that and reward him for it, even if he is wrong. The Prophet says that a scholar who exercises scholarly discretion to arrive at a ruling will be given a double reward if he is right and a single reward if he is wrong.