“I once sent (a letter) to abu ‘Abd Allah (a.s.), to find out when Zakat becomes obligatory for the assets of my small brothers. He (the Imam) said, ‘When Salah (prayer) becomes obligatory up on them, Zakat also become obligatory; however, in the case of those of them on whom Salah (prayer) is not obligatory but their asset is used in business, you must pay Zakat for such assets.’”