Guru nanak dev ji was the first of the ten sikh gurus and the founder of sikhism. The birthday of guru nanak dev ji is observed as "Guru nanak gurpurab" Across the globe. He is considered as one of the august religious thinkers ever. He who regards all men as equals is religious. 
Asceticism doesn't lie in mere words. He is an ascetic who treats everyone alike. Asceticism doesn't lie in visiting burial places. It lies not in wandering about nor in bathing at places of pilgrimage. Asceticism is to remain pure amidst impurities. 