Sant Namdev was one of the pillars of the Bhakti cult that developed around the worship of Bhagavan Vitthal of Pandarpur in Maharashtra during the middle ages. Story of Namdev and the dog symbolically shows that he was a personification of compassion.
Legend has it that once when Sant Namdev had sat down for his routine meal of Dal Roti with a dash of ghee to go with it, all of a sudden; a dog appeared and, snatching a roti, ran away.
Namdev got up hurriedly and, grabbing the small container holding the ghee, ran after the dog, hailing it, “O Lord! How will you eat the dry roti all by itself? Please take this ghee with it!
Sant Namdev, who saw God in everything, including the dog, ran after Him. The sweetness with which he addressed the canine and the compassion behind his action reveals the sensitivity of evolved souls, who see creation as an extension of themselves.
Source - My Mother, My Master By Swami Pranavamritananda Puri