Or HaChaim on Genesis 37:18/אור החיים על בראשית ל״ז:י״ח

1"And they saw him afar off" It is necessary to know, when saying "and before" (Gen. 37:18), whether it applies to what was before it, as follows: 'And they saw him afar off before he came near to them' or if it [namely, the word "before"] is the beginning of what comes afterwards, as follows: 'Before he came near to them they conspired regarding him...' Both interpretations are difficult: if it applies to what was before it, it should have said 'before he came near' [not AND before he came near], and if it is the beginning of what comes afterwards, it should have said 'and before...they conspired' [not AND they conspired]. Maybe the addition of the vav was meant to increase distance, meaning that you shouldn't say that the distance implies that he [Joseph] has not yet approached them [his brothers], rather "and before he came near to them" means they saw him at an exaggerated distance.

2We could say further that "and they saw him from afar off" refers to the distance of their hearts, because they did not see him as brothers see their brothers, rather, they saw him like a man distant from them; "and before he came near..." means that this seeing was also "before..." and if it hadn't said "And before" with a vav it would have implied the reading of distance above [namely that they saw Joseph at a great physical distance], therefore the vav was added, to show that the matter was different [namely that the distance was emotional]. One could also offer a different explanation of the text, but it appears that this is the best reading.