Christians - Guess who said this?

Here's the quote, which was addressed to children. Post your guess. 10 points goes to the first person who guesses correctly. Answer will be revealed later today.

(P.S. Non-Christians also welcomed to guess, but the person being quoted is a well-known Christian, so you might not recognize it)

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"Friendship with Jesus is such a beautiful gift that you cannot keep it to yourselves! Those who receive this gift feel the need to give it to others; and in this way the shared gift does not diminish but multiplies! Keep to this path! You are growing up and soon you will become adolescents and young people. Do not lose your missionary spirit. Always keep your faith pure and genuine..."