The inquirer's granddaughter was born with her left hand missing below the elbow. The doctor advised to have her fitted with prosthesis when she turns four. Is this permissible or is it considered objecting to Allah's will?
Allah the Almighty created man in the best form from clay. He breathed life into him of His spirit and equipped him with the faculty of seeing and understanding. Allah the Almighty says,
He Who created All things in the best way and He began the creation of man from clay, and made his progeny from a quintessence of despised fluid. But He fashioned him in due proportions, and breathed into him of His spirit. And He gave you (the faculties of hearing and sight and understanding little thanks do ye give! [Al-Sajda: 7-9]
Allah the Almighty knows the developments that take place inside a woman's womb i.e. the increase or decrease in the period of gestation, the number of embryos, and defects, if any; He creates everything in just measure and proportion. He says,
Allah doth know what every female (womb) doth bear, by how much the wombs fall short (of their time and number) or do exceed. Every single thing is with Him in (due) proportion. He knoweth the Unseen and that which is open: He is the Great, the Most High. [Ar-Ra'd: 8-9]
Allah the Almighty is fully aware of His creation; He is the Creator — He creates what He wills and chooses for His creation what He wills,
Thy Lord does create and choose as He pleases: no choice have they (in the matter): Glory to Allah! And far Is He above the partners they ascribe (to Him). [Al-Qasas: 68]
He creates males and females, the sick and healthy, the tall and short, the white and black, all for a wisdom only known to Him. He is the sole Knower of the unseen. Allah the Almighty says,
With Him are the keys of the Unseen, the treasures that none knoweth but He. He knoweth whatever there is on the earth and in the sea. Not a leaf doth fall but with His knowledge: There is not a grain in the darkness (or depths) of the earth, nor anything fresh or dry (green or withered), but is (inscribes) in a Record Clear (to those who can read). [Al-An'am: 59]
Verily, the knowledge of the Hour is with Allah (alone). It is He Who sends down rain, and He Who knows what is in the wombs. Nor does anyone know what it is that he will earn on the morrow: Nor does anyone know in what land he is to die. Verily, with Allah is full knowledge and He is acquainted (with all things). [Luqman: 34]
A person born with an anomaly is obliged to treat it. 'Abdullah reported that the Prophetsaid, "Allah did not make a disease without making a cure for it" [Ibn Majah].
There is no objection to resorting to prosthesis in the absence of a cure. It has been reported that after 'Arjafa lost his nose in the battle of Kilab, the Prophetordered him to use a prosthesis made of gold instead of the paper one he used which had developed a stench [recorded by Abu Dawud, al-Nisa`i and at-Tirmidhi].
It is permissible for the inquirer to have her newborn granddaughter fitted with a prosthetic hand.
Allah the Almighty knows best.