"That he might, for his own dear sake, become a Partaker, a Partner in them; and then, thought I, when we can Hand in Hand, Heart in Heart, one Spirit, as well as one Flesh, join in the same Closet, in the same Prayers and Thanksgivings, what an happy Creature shall I be!"
— Richardson, Samuel (bap. 1689, d. 1761)
First edition published in two volumes on 6 November, 1740--dated 1741 on the title page. Volumes 3 and 4 were published in December 7, 1741 (this sequel is sometimes called Pamela in her Exalted Condition).
See Samuel Richardson, Pamela: or, Virtue Rewarded. In a Series of Familiar Letters from a Beautiful Young Damsel, to Her Parents: Now First Published in Order to Cultivate the Principles of Virtue and Religion in the Minds of the Youth of Both Sexes. A Narrative Which Has Its Foundation in Truth and Nature: and at the Same Time That It Agreeably Entertains, by a Variety of Curious and Affecting Incidents, Is Intirely Divested of All Those Images, Which, in Too Many Pieces Calculated for Amusement Only, Tend to Inflame the Minds They Should Instruct (London: C. Rivington and J. Robinson, 1740). [Title page says 1741] <Link to ESTC><Link to ECCO><Link to first vol. of 3rd edition in ECCO-TCP>
See also Pamela: or, Virtue Rewarded. in a Series of Familiar Letters from a Beautiful Young Damsel to Her Parents: and Afterwards, in Her Exalted Condition, Between Her, and Persons of Figure and Quality, Upon the Most Important and Entertaining Subjects, in Genteel Life. the Third and Fourth Volumes. Publish’d in Order to Cultivate the Principles of Virtue and Religion in the Minds of the Youth of Both Sexes. by the Editor of the Two First. (London: Printed for S. Richardson: and sold by C. Rivington, in St. Paul’s Church-Yard; and J. Osborn, in Pater-Noster Row,  ). <Link to ESTC>
All searching was originally done in Chadwyck Healey's eighteenth-century prose fiction database through Stanford's HDIS interface. Chadwyck-Healey contains electronic texts of the original editions (1740-1741) and the 6th edition (1742).