Daily Reading: Srimad Bhagavatam page-58

SB 1.3.11

ṣaṣṭham atrer apatyatvaṁ
 vṛtaḥ prāpto ’nasūyayā
ānvīkṣikīm alarkāya
 prahlādādibhya ūcivān

Translation: 

The sixth incarnation of the puruṣa was the son of the sage Atri. He was born from the womb of Anasūyā, who prayed for an incarnation. He spoke on the subject of transcendence to Alarka, Prahlāda and others [Yadu, Haihaya, etc.].

Purport: 

The Lord incarnated Himself as Dattātreya, the son of Ṛṣi Atri and Anasūyā. The history of the birth of Dattātreya as an incarnation of the Lord is mentioned in the Brahmāṇḍa Purāṇa in connection with the story of the devoted wife. It is said there that Anasūyā, the wife of Ṛṣi Atri, prayed before the lords Brahmā, Viṣṇu and Śiva as follows: “My lords, if you are pleased with me, and if you desire me to ask from you some sort of blessings, then I pray that you combine together to become my son.” This was accepted by the lords, and as Dattātreya the Lord expounded the philosophy of the spirit soul and especially instructed Alarka, Prahlāda, Yadu, Haihaya, etc.

SB 1.3.12

tataḥ saptama ākūtyāṁ
 rucer yajño ’bhyajāyata
sa yāmādyaiḥ sura-gaṇair
 apāt svāyambhuvāntaram

Translation: 

The seventh incarnation was Yajña, the son of Prajāpati Ruci and his wife Ākūti. He controlled the period during the change of the Svāyambhuva Manu and was assisted by demigods such as His son Yāma.

Purport: 

The administrative posts occupied by the demigods for maintaining the regulations of the material world are offered to the highly elevated pious living beings. When there is a scarcity of such pious living beings, the Lord incarnates Himself as Brahmā, Prajāpati, Indra, etc., and takes up the charge. During the period of Svāyambhuva Manu (the present period is of Vaivasvata Manu) there was no suitable living being who could occupy the post of Indra, the King of the Indraloka (heaven) planet. The Lord Himself at that time became Indra. Assisted by His own sons like Yāma and other demigods, Lord Yajña ruled the administration of the universal affairs.