His boss gave him the job of following up on some technical drawings, and he managed to save some money on that

Question

Praise be to Allah.

Firstly:

The ruling in this case depends on knowing the nature of the
agreement that was made between the boss and your colleague. If the
agreement between them was that your colleague would look for someone to do
these drawings, and he agreed with the boss on the money to be paid for that
job, then he was to find someone who would do the job for whatever amount
they agreed, then if any of that money is left over, it belongs to him, and
if the cost was greater, then he is to pay the extra. This is permissible
and there is nothing wrong with you taking the money that your colleague
gave you. In this case your colleague is like a contractor who takes on the
job, then assigns it to the one who will do it.

But you stated that the agreement was based on the idea that
he was going to work with the engineers abroad, and that you told your
colleague about local engineers. There is nothing wrong with that, so long
as the boss does not care who does the work, rather what he cares about is
that the work should be done to the required specifications only.

But if the boss wanted the work to be done with a specific
office or engineer, or he specified that the work should be done outside the
Kingdom so that company secrets would not be divulged and cause some
problems and the like, then it is essential to fulfil what was agreed, and
it is not permissible to go against it.

If the agreement between them is that your colleague was just
the middleman between the boss and the engineers, and was not to make any
profit from this work, then he is acting as the agent of the boss, and the
agent does not have the right to make money from the one who appointed him
except with his knowledge. In that case, your colleague has to tell the boss
what really happened, and that those who are going to do the work are
engineers inside the Kingdom, not abroad, and he has to return to him the
surplus money.

Secondly:

If the work that your colleague is doing is haraam, in the
way mentioned above, it is not permissible for you to help him, either by
telling him about engineers or any other kind of help. Rather you should
advise him to fulfil the trust and to avoid consuming that which is not
permissible for him.

With regard to what you did of phone calls, following up and
making appointments, if you did that with the intention of going back to
your colleague and asking for the usual payment for such work, then you may
do that. But if you did it voluntarily, you do not have the right to ask for
anything, but if he gives you something in this case willingly, we do not
think that you should take it, unless he has cleared the matter with the
boss and he has let him keep the money saved.

And Allah knows best.