The Story of Upali

On one occasion, Upali the millionaire, a follower of Nigantha Nataputta, approached the Buddha and was so pleased with the Buddha's exposition of the Dhamma that he instantly expressed his desire to become a follower of the Buddha. But the Buddha advised him, saying--"Of a verity, O householder, make a thorough investigation. It is well for a distinguished man like you to make a thorough investigation." 

Upali, who was overwhelmed with joy at this unexpected utterance of the Buddha, said: "Lord, if I had become a follower of another teacher, his followers would have taken me round the streets in procession proclaiming that such and such a millionaire had renounced his former religion and had embraced theirs. But, Lord, you advise me to investigate further. The more pleased am I with this salutary advise of yours." And he appreciatively repeated -- for the second time, "I seek refuge in the Buddha, the Dhamma, and the Sangha."

Though Upali became a Buddhist by conviction, the Buddha, quite in keeping with his boundless compassion and perfect tolerance, advised him to support his former religious teacher in accordance with his practice.

 (As told by Ven. Narada in The Buddha and His teachings) 

(From: Once Upon a Time - A Collection of Buddhist Stories)