Once when Guru Nanak came to the small town of Saidpur in West Punjab he choose to stay there with Lalo, a low caste carpenter. At the same time the local chief of the town Malik Bhago, who was quite wealthy and a very proud man was holding a feast to which all holy men were invited. When Malik Bhago found out that Guru Nanak would not attend his feast but instead partook of the simple fare of his host Lalo, he was quite angry and had the Guru brought to him for questioning. When asked why he didn't join in the feast, the Guru sent for the meal served by Malik Bhago and also some of the simple meal served by Lalo.
Holding these in separate hands he squeezed them, blood appeared out of the rich food of Malik Bhago, while milk oozed out of Lalos simple fare. Malik Bhago was put to shame and realized that his riches had been amassed by exploiting the poor, while what Lalo offered was the milk of hard earned honest work.
Another time while camped out at a town during the rainy season, several devotees would come to the Guru on a regular basis. One of them while on the way to see the Guru, came across a prostitute and was allured by her. Thereafter he would leave home on the pretext of going to see the Guru, but instead visited the prostitute. A few days later his friend who daily came to pay homage to the Guru was pricked by a thorn, while his neighbor, who visited the prostitute, found a gold coin in the street.