There are two ways of association – by vani and by vapuh. Vani means words, and vapuh means physical presence. Physical presence is sometimes appreciable and sometimes not, but vani continues to exist eternally. Therefore we must take advantage of the vani, not the physical presence. The Bhagavad-gita, for example, is the vani of Lord Krsna. Although Krsna was personally present five thousand years ago and is no longer physically present from the materialistic point of view, the Bhagavad-gita continues.
(Srila Prabhupada: Cc Antya Concluding Words)