Dave Ramsey mentioned this later on a recent podcast episode (which could have been a repeat) and so I looked it up.  It can be found online in a collection of his writings here.  However, I thought you might like to read the letter because it is quite interesting to see Abe’s approach to helping his family.

Dear Johnston, Your request for eighty dollars I do not think it best to
comply with now. At the various times when I have helped you a little
you have said to me, “We can get along very well now”; but in a very
short time I find you in the same difficulty again. Now, this can only
happen by some defect in your conduct. What that defect is, I think I
know. You are not lazy, and still you are an idler. I doubt whether,
since I saw you, you have done a good whole day’s work in any one day.
You do not very much dislike to work, and still you do not work much,
merely because it does not seem to you that you could get much for it.
This habit of uselessly wasting time is the whole difficulty; it is
vastly important to you, and still more so to your children, that you
should break the habit. It is more important to them, because they have
longer to live, and can keep out of an idle habit before they are in it,
easier than they can get out after they are in.

You are now in need of some money; and what I propose is, that you shall
go to work, “tooth and nail,” for somebody who will give you money for
it. Let father and your boys take charge of your things at home,
prepare for a crop, and make the crop, and you go to work for the best
money wages, or in discharge of any debt you owe, that you can get; and,
to secure you a fair reward for your labour, I now promise you, that for
every dollar you will, between this and the first of May, get for your
own labour, either in money or as your own indebtedness, I will then
give you one other dollar. By this, if you hire yourself at ten dollars
a month, from me you will get ten more, making twenty dollars a month
for your work. In this I do not mean you shall go off to St. Louis, or
the lead mines, or the gold mines in California, but I mean for you to
go at it for the best wages you can get close to home in Coles County.
Now, if you will do this, you will be soon out of debt, and, what is
better, you will have a habit that will keep you from getting in debt
again. But, if I should now clear you out of debt, next year you would
be just as deep in as ever. You say you would almost give your place in
heaven for seventy or eighty dollars. Then you value your place in
heaven very cheap, for I am sure you can, with the offer I make, get the
seventy or eighty dollars for four or five months’ work. You say if I
will furnish you the money you will deed me the land, and, if you don’t
pay the money back, you will deliver possession. Nonsense! If you can’t
now live with the land, how will you then live without it? You have
always been kind to me, and I do not mean to be unkind to you. On the
contrary, if you will but follow my advice, you will find it worth more
than eighty times eighty dollars to you.

I guess we could call this a guest post by Abraham Lincoln