Fiqh-us-Sunnah Volume 3, Zakaat and Fasting, Fiqh 3.058A.
The opinion of Malik, al-Auza’i, Ishaq, Ahmad, and Abu ‘Ubaid is that whoever possesses a nisab of any kind of property and then sells it before the completion of the year hawl, or gives it away as a gift, or damages part of it with the intention of avoiding its zakah, he still must pay its zakah. If he engages himself in any of the preceding acts at a time when his obligation to pay zakah is about to mature, he will be forced to pay it. If, however, any of the preceding acts happen at the beginning of the hawl, this will not constitute an evasion, and he will be (legally) free from his obligation to pay zakah.
Abu Hanifah and ash-Shaf’i hold that since the amount decreased before the end of the hawl, zakah will not be paid on it. He would still be considered a wrongdoer and disobedient to Allah for attempting to escape it. The early Muslims based their rationale on the ‘ayahs in which Allah, the Exalted One, says: “Lo! We have tried them as We tried the owners of the garden when they vowed they would pluck its fruit the next morning, and made no reservation [for the will of Allah]. Then a visitation from your Lord came upon it while they were asleep. So the garden became a dark and desolate spot in the morning, as if it were plucked” [alMulk 17-20]. Allah punished those people for avoiding their obligation to the poor.
Zakah, as such, will still be due and the person has to pay it because his intention was to deprive the poor of their share in his wealth. This would be similar to the case of a man who divorces his wife during his terminal illness. His evil intention calls for punishment as a redemptive act. Another case of a similar nature would be that of a person who kills his benefactor so that he could have his inheritance. In that case, Allah punishes him by depriving him of his inheritance.