What does the quote "One must find the source within one's own Self, one must possess it" mean?

Siddhartha calls himself the "seeker of truth." The quote you've been given isn't complete, so it may not have the same feel when taken out of context, and the quote in its entirety actually refers to his father: “Was Atman then not within him? Was not then the source within his own heart? One must find the source within one’s own Self, one must possess it. Everything else was seeking – a detour, error.”

Whar we hear in this quote is the root of Siddharth'a personal faith, and although he doesn't actually reach completely until the end of the novel this is where we see its roots. During the first two sections of the story, Siddhartha is heavily influences by his teachers and their teachings (like all children, and even as an adult he continues to learn. The quote he uttered as a young man refers to journeying the path of enlightenment; he reaches this stage in the end at the river.