Marcelino Menéndez Pelayo called him la lumbrera intelectual de su siglo ("the brightest intellect of his age").
On 5 February 1682 he took the Benedictine habit at the monastery of San Pedro de Cardeña, making his profession a short while later, on 21 March.
He was shortly thereafter sent to study at San Vicente de Salamanca, where he spent twelve years before returning to Cardeña.
As a historian he was innovative and modern, rejecting traditional methods of historical inquiry, he turned to the direct study of the documents.
His Antigüedades de España brought to light many documents, including many from the archives of Cardeña, that had not until then been publicised.