When there is in the śāstra nirākāra, this word is used, nirākāra means He has no prakṛta-ākāra, material form. That is nirākāra, not that He has no form. That is poor fund of knowledge. He is sac-cid-ānanda-vigraha (Bs. 5.1). Therefore Kṛṣṇa says in the Bhagavad-gītā, avajānanti māṁ mūḍhā mānuṣīṁ tanum āśritam (BG 9.11): "My original form is like human being." And the Bible also it is said, "Man is made after the form of the God."
So God has a form just like a human being, two hands, two legs, and He Himself comes to show Him. That is Kṛṣṇa. He is not nirākāra. Īśvaraḥ paramaḥ kṛṣṇaḥ sac-cid-ānanda-vigrahaḥ (Bs. 5.1). Vigraha. Vigraha means form. Īśvaraḥ paramaḥ kṛṣṇaḥ sac-cid-ānanda-vigrahaḥ. Avyaktaṁ vyaktim āpannaṁ manyante mām abuddhayaḥ (BG 7.24). That is stated in the Bhagavad-gītā. You know. Avyaktaṁ vyaktim āpannam: "The original is impersonal Brahman. Now He has taken form." This conclusion, who makes? Avyaktaṁ vyaktim āpannaṁ manyante mām abuddhayaḥ: "Those who are less intelligent, whose intelligence is very poor, they consider that ultimately I am nirākāra. I have taken the form." Sākāra-nirākāra.
No. Kṛṣṇa says, sambhavāmy ātma-māyayā (BG 4.6): "I come out of My good will." Yadā yadā hi dharmasya glānir bhavati bhārata, tadātmānaṁ sṛjāmy aham (BG 4.7): "At that time I appear."