לזכות אבי מורי ואמי מורתי שיחיו
The Halacha is that if one finds a lost object and is busy with it, he need not give tzdaka at that time. The question is if an עני is coming and he finds a lost object. Is it permitted for him to go take care of the object even though he knows that it will prevent him from giving the tzdaka?
Also, is it permitted to take care of an object before זמן קריאת שמע and תפילה, if as a result, he will miss them?
The Ritva asks why we need a pasuk to prove that עוסק במצוה פטור מן המצוה? OF COURSE you need not stop mitzva "a" to perform mitzva "b"?!
He answers that the pasuk tells us that not only is one not OBLIGATED to stop doing the present mitzva but one is actually FORBIDDEN from stopping and performing the second mitzva.
He offers another answer: The pasuk is teaching us that that even though there is a set mitzva at a set time that is about to present itself, nevertheless, he may start the mitzva regardless of the consequences of missing the set mitzva.
From this second answer we see that even if he knows that the עני is about to come, he should still take care of the lost object.
However, we can prove the other way: If one is busy with taking out a מת he is פטור from קריאת שמע, because עוסק במצוה פטור מן המצוה.
The Shulchan Aruch [72-2] says that if the time for שמע hasn't yet arrived, then one may not take out the מת for burial until he has read שמע [however, if he already started he need not stop].
We see that one may not start a mitzva [if he can do it afterward], when he knows that he will become פטור from another מצוה as a result because of the rule עוסק במצוה פטור מן המצוה.
[מאוצרות הגר"א גנחובסקי זצ"ל]
