SB 1.3 - The multi forms of the Lord are one
Since there are many different avatāras and Kṛṣṇa Himself has two-armed and four-armed forms, and as well displays ages such as kaumāra and kaiśora, and they are all said to be eternal, still it does not mean there are many Gods. SB 10.40.7 says He is one God manifested as many. The jīva at different times in saṁsāra shows different temporary forms with less or more power, but the one Supreme Lord by His inconceivable energy can simultaneously have infinite eternal forms which are not different from Him. The jīvas show infinite variety simply because there are infinite jīvas. The Lord shows infinite variety of forms by being one person. Thus when the jīva sees the Lord, he perceives the Lord as if there are many Lords, like jīvas.
The Mahā-varāha Purāṇa says that all the forms of the Lord are eternal, appearing constantly within the material world with bodies of Paramātmā, without any destructible elements made of prakṛti. Though the forms are perfect and complete, they are called aṁśa because they display only various degrees of the Lord’s qualities such as sweetness, power and mercy. Real completeness means fully displaying all the powers which takes place in the aṁśī. And SB 3.8.4 also says that Lord Saṅkarṣaṇa meditates upon His Supreme Lord, Vāsudeva. There is nothing contradictory if there are differences between the aṁśī and aṁśa, since the Lord is spiritual substance. There are two types of aṁśas, the expansions of the Lord and the jīvas.
Whoever carefully recites the mysterious appearances of the Lord, with devotion in the morning and in the evening, gets relief from all miseries of life. In the gītā it is said that one who knows the principles of the transcendental birth and activities of the Lord will go back to Godhead after leaving one’s body. Thus the birth and activities of the Lord are not ordinary. Only one who goes deep into the matter by spiritual devotion can understand the mystery of the Lord.