Here are some select suggestions (there are many more that could be mentioned), starting with The Book of Psalms. You can find many commentaries on the WCF and HC in the links manager.


Thomas Doolittle, If We Must Aim At Assurance, What Should They Do, That Are Not Able to Discern Their Own Spiritual Condition? in Puritan Sermons, Vol. 1
Thomas Cole, How We May Steer An Even Course Between Presumption and Despair in Puritan Sermons, Vol. 2
Christopher Fowler, How A Christian May Get Such A Faith That Is Not Only Saving, But Comfortable And Joyful At Present in Puritan Sermons, Vol. 2
Joel R. Beeke, Puritan Reformed Spirituality
Joel R. Beeke, The Quest for Full Assurance: The Legacy of Calvin and His Successors
Joel R. Beeke, Assurance of Faith: Calvin, English Puritanism, and the Dutch Second Reformation
John Flavel on Mark 9:24 in Sacramental Meditations upon Divers Select Places of Scripture in his Works, Vol. 6, pp. 378-460 (esp. 426-34)
Robert Asty, A Treatise of Rejoicing in the Lord Jesus in All Cases and Conditions
Thomas Brooks, Heaven on Earth in his Works, Vol. 2
Richard Fairclough, The Nature, Possibility, and Duty, of a True Believer's Attaining to a Certain Knowledge of His Effectual Vocation, Eternal Election, and Final Perseverance to Glory in Puritan Sermons, Vol. 6
Andrew Gray, Three Sermons Concerning the Faith of Assurance in his Works, pp. 183-211
Thomas Hooker, The Poor Doubting Christian Drawn to Christ
Matthew Mead, The Almost Christian Discovered

__________________
Andrew Myers
Husband of Jessica, Father of Jackson, Katie and Samuel
Member, Presbyterian Reformed Church of Northern Virginia
Warrenton, VA USA
Editor, The Matthew Poole Project

"Let your Morning Thoughts, and your last Evening Thoughts, be what shall become of you to all Eternity." -- Matthew Poole