It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) had it written regarding the zakat of cows that when they reach thirty, then a one-year-old calf, male or female, will be obligatory among them. And when their number reaches forty, then a two-toothed animal will be obligatory among them. When the number increases beyond this, then for every forty cows, a two-toothed animal will be obligatory.