Question:

Is it permissible for a person to keep the Zakah of his wealth or Zakatul-Fitr in order to give it to one of the poor people who he is not able to get in touch with yet?

Answer:

If the amount of time is short and not long, there is no harm in him keeping it until he can give it to some of the poor people among his relatives or someone who is poorer or in more dire need. However, it should not be a long period of time. It should only be a number of days that are not numerous. This is in reference to the Zakah of wealth. Concerning Zakatul-Fitr, it should not be delayed for later. Rather, it is obligatory to pay it before the Eid prayer, as the Prophet- Sallallahu alaihi wasallam- ordered. It may be given before the Eid by a day it two or three. There is no harm in that. However, it should not be delayed until after the prayer.

Shaykh `Abdul-`Azeez Bin Baz 

Fatawa Islamiyah Page 205 Vol:2