Musnad Ahmad 175:0

The remainder of the hadith of Ka'b ibn Malik al-Ansari: He said: "When the Messenger of Allah (ﷺ) intended to go out on the campaign of Tabuk, he used to conceal his destination and say: 'I am going to such-and-such a place,' until it was the campaign of Tabuk. The Messenger of Allah (ﷺ) fought it in intense heat, and he faced a long journey, a desert, and a large number of enemies. So he made the situation clear to the Muslims so that they could prepare for their campaign, and he informed them of his destination. The Muslims who went out with the Messenger of Allah (ﷺ) were many, and no book could record them. Ka'b said: 'Any man who wanted to stay behind thought that it would remain hidden from him, as long as no revelation came down from Allah regarding it.' The Messenger of Allah (ﷺ) fought that campaign when the fruits had ripened and the shade was pleasant, and I inclined towards them. The Messenger of Allah (ﷺ) and the Muslims with him prepared, and I began to go out to prepare with them, but I returned without having done anything. I would say to myself: 'I am able to do that if I want.' This continued until the people departed, and the Messenger of Allah (ﷺ) and the Muslims with him set out, while I had not prepared anything. I said: 'I will prepare after them for a day or two, then I will catch up with them.' So I went out in the morning to prepare, but I returned without having done anything. Then I went out again, and I returned without having done anything. That continued until they hastened and the matter became urgent, and they departed. I wanted to go out and catch up with them—and I wish I had done so—but it was not decreed for me. After the Messenger of Allah (ﷺ) had departed, I would go out among the people and it would grieve me that I saw no one except a man suspected of hypocrisy or a man whom Allah had excused among the weak."