Which one is correct?
1. I had left my wallet at home. Luckily, my friend Ahmed was passing
by and lent me some money.
2. I had left my wallet at home. Luckily, my friend Ahmed passed
beside me some money.

Question

Which one is correct?
 1. I had left my wallet at home. Luckily, my friend Ahmed was passing 
     by and lent me some money.
 2. I had left my wallet at home. Luckily, my friend Ahmed  passed 
     beside me some money.

Answer

The first one is correct. The second sentence is grammatically correct whereas in #2, there are some words missing to make the phrase complete. For example, you could say "...Ahmed passed me and lent (or gave) me some money." I would remove "beside" as it's redundant (don't need it when "passed" suffices for where the friend is in relation to you) and put "and lent" (or "and gave") to make clearer what happened when you happened to meet your friend. I hope this helps. :-)