أُجِيبُ دَعْوَةَ الدَّاعِ إِذَا دَعَانِ فَلْيَسْتَجِيبُوا لِي
I answer the supplicant when he calls on Me; so let them respond to Me.
Ajību and yastajībū share a response-related semantic family, but the agents and directions differ. God responds to the caller; the servants are then urged to respond to God. The relationship is lexical as well as conceptual.
Stopping at the shared root would miss the progression from human supplication to divine response and back to human responsiveness. Formal resemblance is meaningful here because it serves the larger sequence.