大乘起信論義記 1.44

1.44

初盡十方者，明所敬分齊，然有二義：一云、非直歸於一方三寶，乃欲盡於十方齊敬。二云、於十方內非直各歸一二等剎，亦乃一一方所各盡彼方無盡世界一切三寶。何以爾者？顯三寶普遍故、敬心廣大故、簡異小乘故、為論幖幟故，故盡十方也。

First, "exhausting the ten directions" clarifies the scope of what is revered, which however has two meanings: first, it means not merely taking refuge in the three jewels of one direction, but rather intending to pay homage equally throughout all ten directions. Second, it means that within the ten directions, one does not merely take refuge in one or two realms each, but rather, in each and every direction, one exhausts all the three jewels of the endless worlds of that direction. Why is this so? To show that the three jewels are all-pervading, that the mind of reverence is vast and great, to distinguish this from the Hīnayāna, and to serve as an emblazonment of the treatise; therefore it says "exhausting the ten directions".