Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 35
नाहं भक्षितवानम्ब सर्वे मिथ्याभिशंसिन: ।यदि सत्यगिरस्तर्हि समक्षं पश्य मे मुखम् ॥ ३५ ॥
nāhaṁ bhakṣitavān ambasarve mithyābhiśaṁsinaḥyadi satya-giras tarhisamakṣaṁ paśya me mukham
Lord Śrī Kṛṣṇa replied: My dear mother, I have never eaten dirt. All My friends complaining against Me are liars. If you think they are being truthful, you can directly look into My mouth and examine it.
Kṛṣṇa presented Himself as an innocent child to increase the transcendental ecstasy of maternal affection. As described in the śāstra, tāḍana-bhayān mithyoktir vātsalya-rasa-poṣikā. This means that sometimes a small child speaks lies. For example, he may have stolen something or eaten something and yet deny that he has done so. We ordinarily see this in the material world, but in relation to Kṛṣṇa it is different; such activities are meant to endow the devotee with transcendental ecstasy. The Supreme Personality of Godhead was playing as a liar and accusing all the other devotees of being liars. As stated in Śrīmad-Bhāgavatam (10.12.11), kṛta-puṇya-puñjāḥ: a devotee may attain such an ecstatic position after many, many births of devotional service. Persons who have amassed the results of a vast amount of pious activities can attain the stage of associating with Kṛṣṇa and playing with Him like ordinary playmates. One should not consider these transactions of transcendental service to be untruthful accusations. One should never accuse such devotees of being ordinary boys speaking lies, for they attained this stage of associating with Kṛṣṇa by great austerities (tapasā brahmacaryeṇa śamena ca damena ca).