Islamic Laws according to the Fatawa of Ayatullah al Uzama Syed Ali al-Husaini Seestani from English Version of Taudhihul Masae'l
1965. * A person should give Zakat with the intention of Qurbat, that is, to comply with the pleasure of Almighty Allah. And he should specify in his Niyyat, whether he is giving the Zakat on his wealth, or Zakatul Fitra. Also, if it is obligatory on him to give Zakat on wheat and barley, and if he wants to pay a sum of money equal to the value of Zakat, he should specify whether he is paying in lieu of wheat or barley.
1966. * If a person becomes liable to pay Zakat on various items, and he gives a part of Zakat without making Niyyat of any of those items, if the thing which he has given is of the same class as any one of those items, it will be reckoned to be Zakat on that very commodity. For instance, if it is obligatory on a person to pay Zakat on 40 sheep and on 15 mithqals of gold, and he gives one sheep as Zakat without any specified Niyyat of either, it will be treated to be Zakat on sheep. But if he gives some silver coins or bank notes, which does not belong to either class, as it is neither sheep nor gold, it is a matter of Ishkal and the Zakat will not be considered as paid.
1967. If a person appoints someone as his representative to give away the Zakat of his property, he should, while handing over Zakat to the representative, make Niyyat that whatever his representative will later give to a poor is Zakat. And it is better that his Niyyat remains constant till Zakat reaches the poor.
1968. * If a person gives Zakat to poor, or to the Mujtahid, without making the Niyyat of Qurbat, it will be accepted as Zakat, although he will have committed a sin for not having the Niyyat of Qurbat.