The subject comes from various early church fables collected by Jacobus de Voragine in his Golden Legend of c.1260. The apostles were brought by angels to the Virgin's death-bed and assisted in her burial in a tomb in the Vale of Josaphat; there she was assumed (that is, 'carried up'), body and soul, into heaven, 'great multitude of angels keeping her company'. St John of Damascus (c.675–c.749) called the Virgin the 'font of true light' and likened her assumption to the sun appearing after an eclipse. Rubens uses a similar metaphor, creating a heavenly glory around the Virgin in the likeness of the rising sun. Rubens departs from usual practice in including the sisters, Sts Mary and Martha, symbols of the active and contemplative life, with the apostles round the tomb.

This was one of two presentation oil sketches (modelli) which Rubens made in 1611 in a bid to secure the commission to paint the Assumption of the Virgin for the high altar of Antwerp Cathedral. The other is in the Hermitage Museum; the final altarpiece, which Rubens did not deliver until 1620, is now in the Kunsthistorisches Museum in Vienna. Obviously the nuns of the church did not make a simple choice of one or the other design, but went rather for a mix-and-match of elements: the upper half largely following the oil sketch in the Royal Collection and the lower half that in the Hermitage. The only problem with this explanation is that this oil sketch has appeared to many scholars to be later in date than its Hermitage counterpart, though when they were hung together in the National Gallery's 2005 Rubens: Master in the Making exhibition, it seemed quite possible that they were painted at the same time. If these two oil sketches were presented as alternatives, then that provides a valuable insight into the kind of changes Rubens felt that he could ring. The iconography differs: this is an Assumption; the Hermitage painting a Coronation with music-making angels; this one has a sarcophagus tomb, that a cave in the rock. The most interesting variation occurs in the lighting: the Hermitage panel shows a torch-lit, nearly night scene with a golden heaven; this panel shows a naturally lit evening scene with an azure heaven. Blue is the keynote colour here, suggestive of a luminous sky and symbolic of heaven. The Virgin here wears white to symbolise purity; she is usually shown wearing a blue cloak alluding to her status as Queen of Heaven. It is this symbolic blue that has somehow permeated every centimetre of this panel.

The other talent, which Rubens would wish his patrons to appreciate here, is variety. Twelve apostles witness the same event and yet Rubens finds twelve different postures and emotions for them to adopt. The tangle of baby angels teases (literally amazes) the eye like a knot – as, in a different way, do the innumerable angel heads merging with clouds. For William Hogarth (1697–1764) one of the pleasures of painting is that it 'leads the eye a merry kind of chace'. But here this complexity has a spiritual meaning: it conveys the 'great multitude of angels', said to be keeping the Virgin company in her assumption, and more generally the idea that Heaven is beyond the compass of the human mind. Rubens's source is the Assumption of the Virgin painted on the dome of the cathedral in Parma in the 1530s by Correggio (c.1489–1534). A similar effect in the dome of S. Andrea della Valle in Rome painted by Lanfranco (1582–1647) in 1624 was described by Bellori as being like the sounds of a full choir where you appreciate the total effect without being able to distinguish the individual voices.