الَّذِي أَطْعَمَهُم مِّن جُوعٍ
Who fed them against hunger. (106:4)
The relative expression alladhī describes or further identifies the previously mentioned Lord. Its relative clause recalls a beneficent act, giving the command a readily grasped rationale: the giver of sustenance deserves worship.
A causal rhetorical effect need not always be expressed by an overt causal particle. The syntax may be adjectival while the discourse effect is explanatory or justificatory.