למען ייטב לך ולבניך אחריך עד עולם כי תעשה הטוב והישר בעיני ה' אלקיך ... (יב-כח)
Rashi comments: "הטוב" in the eyes of Hashem, "והישר" in the eyes of people. The obvious question is that the conclusion of this posuk doesn’t seem to jive with this, as it ends "בעיני ה'". So how can Rashi say "והישר" means in the eyes of people?
The first machshava that comes to mind is an oft-used famous principle. Although we have mitzvos בין אדם למקום and בין אדם לחבירו, they are both listed on the same luchos! The implication being that the interpersonal mitzvos must possess the same importance that we afford the mitzvos בין אדם למקום. Essentially, בין אדם לחבירו is also between us and Hashem.
A similar pshat is said in the name of Rabbeinu Ovadia M’Bartenura zt”l. He quotes the well-known Mishna in Pirkei Avos, "כל שרוח הבריות נוחה הימנו, רוח המקום נוחה הימנו". Meaning a person who pleases his fellow man, Hashem is pleased with him as well. And lastly, yet also similar, is a explanation from the Chasam Sofer zt”l. He explains the conclusion of our posuk a bit differently - grammatically כי תעשה הטוב והישר -. When a person does either, למקום OR בין אדם לחבירו, it must be done בעני ה' אלקיך - for the sake of Hashem. Lishma!
Which brings to mind the famous vort on the Gemara in Shabbos. One of the questions a person is asked when standing before the Heavenly Tribunal is, קבעת עתים לתורה - Have you set aside time for Torah learning? One pshat is, that this question is referring to the first eight posukim at the start of the third perek of Koheles. "לכל זמן ועת לכל חפץ תחת השמים". The posuk goes on to enumerate myriad times and intervals in person’s lifetime (עת ללדת, ועת למות...). We are asked: קבעת עתים לתורה? Were you kovea all of your עתים, your precious time, to be governed by the light of our Torah?
May we be zoche to bring הקב"ה much nachas ruach in both areas of בין אדם לחבירו ולמקום.