大毘盧遮那成佛經疏 13.104

13.104

此中如來觀者，言菩薩雖未成佛，而見等同於佛，由見蘊性故得觀名也。唯以悲為體，此悲從離三毒，得無貪等三善根而生成三解脫也，故有三囉字也。

Here, 'Tathāgata-contemplation' means that although the bodhisattva has not yet attained buddhahood, his vision is equal to that of a buddha; because he perceives the nature of the aggregates, he obtains the name 'contemplation' (Avalokita). It takes compassion alone as its essence; this compassion, arising from freedom from the three poisons, attains the three wholesome roots such as non-greed, and generates the three liberations; thus there are three ra syllables.