Beauty ＆ Pure 15

Through the light of a lamp, even darkness that exists a long distance away departs, but the darkness that is present at the foot of the lamp-post is not removed by the lamp. In the same way, those disciples who stay a long way away from the Guru get redeemed by worshipping in their hearts the jnana-Guru who cannot be limited by time or space. Even so, some of those who get the good fortune of staying physically close to the Guru, like his shadow, do not become ripe in jnana, losing their ego-darkness, but die ripe only in physical age. This is due to their immaturity.
Guru Vachaka Kovai v 152

MURUGANAR: The Guru is the shining sun of the Self who removes inner darkness through his true nature. In truth, he is the space of consciousness that has neither rising nor setting. It has therefore been said, ‘the jnana-Guru who cannot be limited by time or space’. The point of the verse if this: those who, through rare good fortune, have reached a jnana-Guru should not forget the purpose for which they came to him. By focusing their entire attention on it day and night, and by taking his grace as the primary support, they should definitely obtain the good fortune of the Self.
Naladiyar says: ‘If he who has obtained the good fortune of associating closely with sages, which cannot be bought by any amount of wealth, spends his time wastefully, he is a person of immature mind.’