Most people are familiar with this expression

and how it informs our view on immigration, treatment of foreigners, of people who are unlike us in one way or another.
What you may not know is that this expression, in one phrasing or another, is repeated many, many times in the Torah. How many? Well, it depends on how you count, some researchers have found more than 40 occurrences, others in the mid-30s and in my own investigation I found 30. Does it matter what the exact number is? In my opinion the answer is No. What matters is that there is no other sentiment that even comes close to this many mentions in the Torah. The conclusion drawn by scholars is that this may be seen as the CENTRAL TENET in Judaism.
Of course, as everything else, this may be a matter of opinion.

I wanted to take it one step further and see who wrote these statements that – unfortunately – has very, very strong contemporary relevance!

Many people are familiar with the authors J, E, P and D and although there are others, for the sake of simplicity, let’s limit it to these 4. Now, did all of these authors state the need of not oppressing the stranger? The answer is actually Yes. But do they emphasize this important Mitzvah (Mitzvah in a broad sense) equally?

I thought it would be interesting to find out. So, using the Sefaria for translation of quotes and Richard Elliott Friedman for designation of who wrote what, here are my results.  
There are two surprising findings:

The low number for J, and the high number for P. All told, the dominating book in this respect is Deuteronomy (Devarim)
So, what can we learn from this?
The centrality of this concept has been discussed in previous articles. What follows are a few references – if you are interested you can read more about this: If you think some of these are repetitive, just think about what’s happening in America today.

-- Can we REALLY say this “too many times?” -- .

/Richard