COMMENTARY on 4:75
A. Yusuf Ali:

Translation:
And why should you not fight in the cause of Allah and of those who, being weak, 592 are ill-treated (and oppressed)?- Men, women, and children, whose cry is: "Our Lord! Rescue us from this town, whose people are oppressors; and raise for us from you one who will protect; and raise for us from you one who will help!" 593
Commentary:

592  Mustad'af=one reckoned weak, and therefore ill-treated and oppressed. (Cf. 4:98, 4:127 and 7:150).

593  Even from the human point of view the cause of Allah is the cause of justice, the cause of the oppressed. In the great persecution, before Makkah was won again, what sorrows, threats, tortures, and oppressions, were suffered by those whose faith was unshaken? Muhammad's life and that of his adherents was threatened: they were mocked, assaulted, insulted and beaten; those within the power of the enemy were put into chains and cast into prison: others were boycotted, and shut out of trade, business, and social intercourse; they could not even buy the food they wanted, or perform their religious duties. The persecution was redoubled for the believing slaves, women, and children after the Hijrah. Their cry for a protector and helper from Allah was answered when Muhammad, the Chosen One, brought freedom and peace to Makkah again.

 

Muhammad Asad:

Translation:
And how could you refuse to fight 89 in the cause of God and of the utterly helpless men and women and children who are crying, "O our Sustainer! Lead us forth [to freedom] out of this land whose people are oppressors, and raise for us, out of Thy grace, a protector, and raise for us, out of Thy grace, one who will bring us succour!"
Commentary:
89  Lit., "what is amiss with you that you do not fight" - implying that they have no moral excuse for such a refusal.