Jean Paul Sartre (1905-1980) – one of the most popular modern thinker stated in a title of his famous essay that existentialism is humanism. I do not want to polemize with such a great author yet in my opinion the humanism begins with a person - and never does with an ideology. Therefore only Jesus can be seen as the holy source of humanism.
Today one may pick and choose from many „-isms”. That's why it is important to make a wise decision when it is comes to decide on a way of living. Prior to the decision always look at the role and place of human being within any philosophical/religious system that seems to be good for you.