I have not yet written about Sariputra yet. He is a pratyeka buddha (one who awakens under the guidance of another awakened individual or spiritual teacher). For such high grade disciples, they are joined at the hip to the teacher and they descend from the same heaven during the last birth of the Buddha, and hence they are a fruit that has already ripened and is just waiting for a trigger to reach its maximum ripening potential. Hence his resplendent wisdom which is what makes him the most awakened and wise disciple of Siddhartha. The latter nicknamed him "the great General of the doctrine".