Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 37
असाध्विदं त्वया कृष्ण कृतमस्मज्जुगुप्सितम् ।वपनं श्मश्रुकेशानां वैरूप्यं सुहृदो वध: ॥ ३७ ॥
asādhv idaṁ tvayā kṛṣṇakṛtam asmaj-jugupsitamvapanaṁ śmaśru-keśānāṁvairūpyaṁ suhṛdo vadhaḥ
[Lord Balarāma said:] My dear Kṛṣṇa, You have acted improperly! This deed will bring shame on Us, for to disfigure a close relative by shaving off his mustache and hair is as good as killing him.
Omniscient Balarāma knew that Rukmī was the guilty party, but to encourage the lamenting Rukmiṇī He decided to gently reproach Śrī Kṛṣṇa