A rule is laid down: one of fewer than ten years' standing may not act as preceptor

The Pali Vinaya records that the monk Upasena, only two years after his own full ordination, conferred full ordination on a pupil of his own, and when the pupil had been ordained a year the two came together to see the Buddha. Having asked their years of standing, the Buddha rebuked him and laid down a rule: one who has not completed ten years since full ordination may not act as preceptor and confer full ordination on others; only those of ten years' standing or more may do so. The Vinaya sub-commentary of the Southern tradition says that the Buddha would not have laid down this rule before ten years had passed since his own awakening, so the rule was laid down in the tenth year after it, and infers that this was at Rājagaha, before the rains retreat at Verañjā in the twelfth year. Source text