The image of entering generation as passing through death's door is seen in the frontispiece of Jerusalem. Blake tells us that we do not enter alone:
Milton, Plate 32 , (E 132) "For God himself enters Death's Door always with those that enter And lays down in the Grave with them, in Visions of Eternity Till they awake & see Jesus & the Linen Clothes lying That the Females had Woven for them, & the Gates of their Fathers House"
Blair's The Grave
William Blake: A Study of His Life
Death to Generation becomes birth to Eternity. The world of generation becomes the 'void outside of existence' which becomes the womb in which the spiritual body is readied for birth to Eternity. Generation has become the image of regeneration.
Jerusalem, Plate 53, (E 203) "Here on the banks of the Thames, Los builded Golgonooza, Outside of the Gates of the Human Heart, beneath Beulah In the midst of the rocks of the Altars of Albion. In fears He builded it, in rage & in fury. It is the Spiritual Fourfold London: continually building & continually decaying desolate! In eternal labours: loud the Furnaces & loud the Anvils Of Death thunder incessant around the flaming Couches of The Twentyfour Friends of Albion and round the awful Four For the protection of the Twelve Emanations of Albions Sons The Mystic Union of the Emanation in the Lord; Because Man divided from his Emanation is a dark Spectre His Emanation is an ever-weeping melancholy Shadow But she is made receptive of Generation thro' mercy In the Potters Furnace, among the Funeral Urns of Beulah"
Four Zoas, Night I, Page 3, (E 301) "Los was the fourth immortal starry one, & in the Earth Of a bright Universe Empery attended day & night Days & nights of revolving joy, Urthona was his name Page 4 In Eden; in the Auricular Nerves of Human life Which is the Earth of Eden, he his Emanations propagated Fairies of Albion afterwards Gods of the Heathen, Daughter of Beulah Sing His fall into Division & his Resurrection to Unity His fall into the Generation of Decay & Death & his Regeneration by the Resurrection from the dead"
Milton, Plate 31 , (E 130) "And all the Living Creatures of the Four Elements, wail'd With bitter wailing: these in the aggregate are named Satan And Rahab: they know not of Regeneration, but only of Generation The Fairies, Nymphs, Gnomes & Genii of the Four Elements Unforgiving & unalterable: these cannot be Regenerated But must be Created, for they know only of Generation These are the Gods of the Kingdoms of the Earth: in contrarious And cruel opposition: Element against Element, opposed in War Not Mental, as the Wars of Eternity, but a Corporeal Strife"
Milton, Plate 41 , (E 142) "These are the destroyers of Jerusalem, these are the murderers Of Jesus, who deny the Faith & mock at Eternal Life: Who pretend to Poetry that they may destroy Imagination; By imitation of Natures Images drawn from Remembrance These are the Sexual Garments, the Abomination of Desolation Hiding the Human lineaments as with an Ark & Curtains Which Jesus rent: & now shall wholly purge away with Fire Till Generation is swallowd up in Regeneration. Then trembled the Virgin Ololon & replyd in clouds of despair Is this our Femin[in]e Portion the Six-fold Miltonic Female Terribly this Portion trembles before thee O awful Man Altho' our Human Power can sustain the severe contentions Of Friendship, our Sexual cannot: but flies into the Ulro. Hence arose all our terrors in Eternity! & now remembrance Returns upon us! are we Contraries O Milton, Thou & I O Immortal! how were we led to War the Wars of Death Is this the Void Outside of Existence, which if enterd into Plate 42  Becomes a Womb? & is this the Death Couch of Albion Thou goest to Eternal Death & all must go with thee"
Jerusalem, Plate 7, (E 150) "Los answer'd... O that the Lamb Of God would look upon me and pity me in my fury. In anguish of regeneration! in terrors of self annihilation: Pity must join together those whom wrath has torn in sunder, And the Religion of Generation which was meant for the destruction Of Jerusalem, become her covering, till the time of the End. O holy Generation! [Image] of regeneration! O point of mutual forgiveness between Enemies! Birthplace of the Lamb of God incomprehensible!" Jerusalem, Plate 62, (E 213) "Jesus replied. I am the Resurrection & the Life. I Die & pass the limits of possibility, as it appears To individual perception. Luvah must be Created And Vala; for I cannot leave them in the gnawing Grave. But will prepare a way for my banished-ones to return"