In the context of proving that the diagonals of rectangle ABCD are congruent, based on the provided statements—AD≅BC, AB≅AB, and ∠DAB≅∠CBA—the next logical statement to include would be about triangles involving vertex O, the intersection of the diagonals.
Given the context, the correct statement that comes next is:
△DAB≅△DOC
Triangle AOD is congruent to triangle BOC.
This statement utilizes the Side-Angle-Side (SAS) postulate, as it confirms that two sides and the included angle of the triangles are congruent, leading to the conclusion that the diagonals are congruent.