The Yarmuk War took place for approximately 3 months, in the year 13 Hijriah. Starting from the caliphate of Abu Bakr and ending during the caliphate of Umar bin Khattab. In this war, the number of Muslim troops was 40 thousand, while the Roman troops numbered 200 thousand. It is said that there was a priest who ordered two Christian people to spy on the Muslim troops. After doing this, these two people told the priest what they had seen, "I have come to bring you news about a gentle people. They ride old and weak horses, at night they are like monks because they are diligent in worship and during the day they are strong horsemen. They were busy repairing arrows and sharpening spears. If you invite your seatmate to talk, he will not understand what you are saying because of the noise of their voices reading the Qur'an and doing dhikr."
So the priest said, "There has come to you a people whom you cannot possibly defeat."
That was the condition of the Muslim troops at that time. Where victory in battle is not just due to the large number of troops, or because of the great equipment used. But because of his closeness to his Rabb. This is truly a very valuable lesson for all of us, so never feel proud of what you have, while you forget what we should have, namely faith and devotion to Allah.