Attributing injustice to Allah is a great sacrilege. Allah has denied oppression from Himself in His Statement:
Truly! Allâh wrongs not mankind in aught; but mankind wrong themselves.
Allah also states in (Part No. 2; Page No. 398) the Hadith Qudsy (Revelation from Allah in the Prophet's words):
O My Slaves, I have made injustice unlawful for Me and made it unlawful for you, so do not wrong one another.
Allah's Decree is entirely based on the perfection of His Wisdom, Justice, Mercy and Knowledge. As for His Slaves being tested with the loss of their children, insufficient provisions, or diseases; this is a trial from Him to distinguish who is patient and pleased with His Decree and those who are not. Allah (Exalted be He) says:
And certainly, We shall test you with something of fear, hunger, loss of wealth, lives and fruits
Then He promised the patient with His Saying:
...but give glad tidings to As-Sâbirûn (the patient).
Who, when afflicted with calamity, say: "Truly! To Allâh we belong and truly, to Him we shall return."
They are those on whom are the Salawât (i.e. who are blessed and will be forgiven) from their Lord, and (they are those who) receive His Mercy, and it is they who are the guided ones.
So, a Muslim should glorify Allah and negate anything that is not befitting of His Majesty. One must be certain that He is Wise and All-Knowing and places all things their proper positions.
He cannot be questioned as to what He does, while they will be questioned.
Whoever attributes injustice to Allah in His Decree over humans and believes this is considered a disbeliever and out of the fold of Islam, because of disbelieving what Allah has informed about denying injustice from Himself. (Exalted is Allah above what they claim). (Part No. 2; Page No. 399) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.