Jonathan Edwards had a son, Timothy Edwards (1738-1813), who left home to study at the College of New Jersey (now called Princeton University). While in Newark, New
Jersey, Timothy became severely sick. To comfort his son, who at that time was only fourteen years old, Jonathan Edwards sent him a letter from Stockbridge, Massachusetts. In this letter Edwards offers a word of prayer for his son and reminds his son of his own duty to pray to God for mercy. Here is an extract from the letter:
Stockbridge, April 1, 1753
My Dear Child,
Before you will receive this letter, the matter will doubtless be determined, as to your having the smallpox. You will either be sick with that distemper, or will be past danger of having it, from any infection taken in your voyage. But whether you are sick or well, like to die or like to live, I hope you are earnestly seeking your salvation….
Till you have savingly believed in Christ, all your desires, and pains, and prayers lay God under no obligation; and if they were ten thousand times as great as they are, you must still know, that you would be in the hands of a sovereign God, who hath mercy on whom he will have mercy. Indeed, God often hears the poor, miserable cries of sinful, vile creatures, who have no manner of true regard to him in their hearts; for he is a God of infinite mercy and he delights to show mercy for his Son’s sake; who is worthy, though you are unworthy; who came to save the sinful and the miserable some of the chief of sinners.
Therefore, there is your only hope; and in him must be your refuge, who invites you to come to him, and says, “He that cometh to me, I will in no wise cast out” [John 6:37]. Whatever your circumstances are, it is your duty not to despair, but to hope in infinite mercy through a Redeemer. For God makes it your duty to pray to him for mercy which would not be your duty, if it was allowable for you to despair. We are expressly commanded to call upon God in the day of trouble; and when we are afflicted, then to pray.
I earnestly desire, that God would make you wise to salvation and that he would be merciful and gracious to you in every respect, according as he knows your circumstances require. And this is the daily prayer of
Your affectionate and tender father, Jonathan Edwards.
P.S. Your mother and all the family send their love to you, as being tenderly concerned for you.
Note: This post is an excerpt from Jonathan Edwards: His Doctrine of & Devotion to Prayer (2013).
 “Letter to Timothy Edwards,” in Letters and Personal Writings, 578-80.