He founded several churches and monasteries. It is also generally agreed that Wales was first divided into dioceses in his time.
Geoffrey of Monmouth states that he died in his monastery at Mynyw i.e., S. David's, where he was honourably buried by order of Maelgwn Gwynedd. This event is recorded by him as if it happened soon after the death of Arthur, who died 542. According to the computations of Archbishop Usher, S. David died 544, aged 82. The Bollandists agree with Usher on the date of his death, but they put his birth back as far as 446, so that according to their calculation he lived to the age of 98.
Numerous legends have gathered round the history of S. David. Thus an angel is said to have foretold his birth thirty years before to his father in a dream. "On the morrow, said the angelic voice, thou wilt slay a stag by a river side, and wild find three gifts there, to wit, the stag, a fish, and a honeycomb. Thou shalt give part of these to the son who shall be born thirty years hence. The honeycomb proclaims his honied wisdom, the fish, his life on bread and water, the stag his dominion over the old serpent." The mention of the stag doubtless arose from the old fancy that that animal kills serpents by trampling on them: thus did David trample the Pelagian heresy under foot. When S. Patrick settled in the vale of Rhos, a voice bade him depart, for it was reserved for the abode of a child who should be born thirty years after.
At his baptism, S. David splashed some water on to the blind eyes of the bishop who was baptizing him, and restored their power of sight. His schoolfellows at "Henmenen" saw a dove teaching him, and singing hymns with him. After studying with Paulinus, he journeyed to Glastonbury. He was intending to dedicate afresh the church which had been re-built, when the Lord appeared to him in a dream, and told him that He had already dedicated it: as a sign that He had spoken unto him He pierced the saint's hand with His fingers. So our saint contented himself with building a Lady Chapel at the east end. He is said to have founded twelve monasteries on this journey. He returned to Wales, and then established a monastery at Mynyw, which was soon filled with monks and disciples. They worked hard with their own hands in the fields; they harnessed themselves to the plough instead of using oxen for that purpose; they tended bees that they might have some honey to give to the sick and the poor. The bees became so attached to one monk, Modemnoc, that they followed him on board ship when he was about to set sail for Ireland. He returned to the monastery and made several attempts to embark unobserved by his winged friends; but all his efforts failed. So at last he asked S. David's leave to take them with him; the saint blessed the bees, and bade them depart in peace, and be fruitful and multiply in their new home. Thus Ireland, where bees had been hitherto unable to live, was enriched by their honey.
He opened many fountains in dry places, healed many brackish streams, raised many dead to life, and had many visions of God and of Angels. In one of these visions he was warned that he should depart, March 1st. Thenceforth he was more zealous in the discharge of his duty: on the Sunday before his death he preached a sermon to the assembled people, and after consecrating and receiving the Lord's Body, he was seized with a sudden pain: then turning to the people he said, "Brethren, persevere in the things which ye have heard of me: on the third day hence I go the way of my fathers." On that day, while the clergy were singing the Matin Office, he had a vision of his Lord; then, exulting in spirit, he exclaimed, "Raise me after Thee." With these words he breathed his last.
He was canonized by Pope Callixtus II., A.D. 1120; who is also said to have granted an indulgence to all those who made a pilgrimage to his shrine. Three kings of England—William the Conqueror, Henry II., and Edward I.—are said to have undertaken the journey, which when twice repeated was deemed equal to one pilgrimage to Rome; whence arose this saying:—
"Roma semel quantum, dat bis Menevia tantum."
A noble English matron, Elswida, in the reign of Edgar, transferred his relics, probably in 964, from S. David's to Glastonbury.
S. David's plain but empty shrine stands now in the choir of S. David's Cathedral to the north of Edward Tudor's altar tomb.