Al-Hajjaj was on a journey between Makkah and Madinah. He pulled out his dinner and invited a bedouin to eat with him, and the bedouin said: “I have been invited by One who is better than you and I have accepted the invitation.” He asked: “And who is this?” The man replied: “Allah invited me to fast, and I fasted.” al-Hajjaj asked: “On this very hot day?” The man replied: “Yes. I am fasting it in anticipation of a much hotter day.” al-Hajjaj said: “So, eat today and fast tomorrow.” The man replied: “Only if you can guarantee that I will live until tomorrow.” al-Hajjaj said: “This isn’t in my hands.” The man said: “How can you ask me to do something now when there is something of the future that isn’t in your hands?”
And Ibn ‘Umar went on a trip once with some companions, and they saw a sheep-herder who they invited to eat with them. He said: “I am fasting,” and Ibn ‘Umar said: “You are fasting in heat like this, and while you are between all these plants and sheep?” The herder replied: “I’m taking advantage of my remaining days.” Ibn ‘Umar was impressed by this reply and said: “Can you sell one of your sheep to us? We’ll feed you from its meat when you break your fast, and we’ll also pay you for it.” The herder said: “It doesn’t belong to me. It belongs to my master.” Ibn ‘Umar said: “What would your master say if you told him that it was eaten by a wolf?” The herder raised his finger to the sky and said: “What about Allah?” Ibn ‘Umar kept repeating this phrase that the herder was saying, and when he got to the city, he went to the herder’s owner and bought him and his sheep from him. He then freed the herder and gave him his sheep as a gift.
Ibn Rajab al Hanbali in ‘Lata’if al-Ma’arif’ (page 272-273)