Syria was one of the colonies of the Roman Empire and its capital was Constantinople. The people were Christians and took orders directly from the Kaiser. On the road leading from Hijr to Damascus there was a strong fort called Tabuk. The Kaiser sent out an army of 4,000 mounted soldiers equipped with the latest armor and weapons to fight the Muslims. The Roman army decided to camp at the fort and await further orders.
When the trade caravans returned to Arabia from Syria, they informed the Holy Prophet (S) that the Romans were gathering an army at the borders of Syria. The Holy Prophet (S) realized that the threat to the Muslim state would have to be stopped, so he sent messages to Makkah and around Madinah asking the Muslims to come to fight in the path of Allah. He also asked the rich people to provide for the expense of war by paying their Zakaat.
At the call of the Holy Prophet (S), 30,000 Muslims gathered near Madinah, ready to participate in battle. 10,000 of these men were mounted soldiers, while the rest were infantry men. At that time it was extremely hot in Madinah. A hypocrite leader called Abdullah bin Ubayy started weakening the spirit of some Muslims by warning them of the great strength of the enemy and the difficulty of marching the long distance to Tabuk in the terrible heat. With his words this hypocrite managed to change the minds of some members of his own tribe, the Khazraj.
The following verse of the Holy Qur'an was revealed at this time.
"They did not wish to strive in Allah's way with their wealth and their selves; and they said (to the others), "Do not go in the heat". Say (O Muhammad), "The fire of Hell is fiercer in heat"; if only they could understand.". Surah at-Tawbah, 9:81The day of departure of the Muslim army arrived, and the Holy Prophet (S) addressed the soldiers to strengthen their morale. Then the army marched out of Madinah towards Tabuk.
The Commander of the Faithful, Imam Ali (A), had always been in the front of every Islamic battle. However, in the Battle of Tabuk, he stayed back in Madinah on the orders of the Holy Prophet (S) himself. The Holy Prophet (S) knew that Tabuk was the farthest place that he had traveled for battle, and that there was a strong chance that anti-Islamic groups might create disturbance in Madinah in his absence.
Although he had appointed Muhammad bin Maslamah to act as his representative, he also left Imam Ali (A) in Madinah to discourage any mischief makers.
The people who had decided to cause trouble in the absence of the Holy Prophet (S), were dismayed at the presence of Imam Ali (A), who was constantly alert. To get Imam Ali (A) out of Madinah, they started a rumor that the Holy Prophet (S) was not happy with him and that was why he had left him behind.
In order to clarify the position Imam Ali (A) followed the Holy Prophet (S) and met him at a place called Jaraf. When the Holy Prophet (S) heard what the hypocrites were saying in Madinah, he uttered a very famous statement that is clear proof of the right of Caliphate of Imam Ali (A).
He said, "O my brother! Return to Madinah, because no one is more suited to preserve the dignity and position of Madinah than myself and you. Don't you feel happy when I say that your relationship with me is similar to the one between Haroon (A) and Musa (A), except that no Prophet will come after me? Just as Prophet Haroon (A) was the immediate successor of Prophet Musa (A), you are my successor and Caliph after me."
The journey of the Muslim army was filled with difficulties and the weather was extremely hot. At one point they ran out of water but there was a heavy shower of rain that brought relief to the advancing army. Finally, the Muslims reached Tabuk but the Romans had already retreated when they received news of the size and strength of the Muslim forces. The Holy Prophet (S) stayed in Tabuk for 20 days and when the enemy did not come back, he decided to return to Madinah.
The journey to Tabuk was not wasted because the Holy Prophet (S) managed to get most of the surrounding chiefs to accept Islam while the others agreed to pay tax to the Muslim state in return for protection. Furthermore, the Romans changed their mind about ever disturbing Muslim territories after having seen the might of the Muslim army.
On the way back, the Holy Prophet (S) passed the valley of Uqba through a narrow hilly road with steep slopes on either side. Huzayfa bin Yamani and Ammar Yasir were helping the Holy Prophet (S) to ensure his safe passage, when suddenly there was some lightning. In the flash of light the Holy Prophet (S) and Huzayfa saw a group of people who were waiting to push the Holy Prophet (S) down the slope. When they were seen, the people ran away. Although their faces were masked, the Holy Prophet (S) told Huzayfa each and every one's identity and asked him never to reveal this knowledge.
The Holy Prophet (S) did not want revenge on these people in case he was accused of killing the people who had helped him to secure power. Since then, Huzayfa was always known as "Keeper of the Holy Prophet's (S) secret."
(Courtesy of:- Shia Ithna asheri Madressa)