Srimad Bhagavatam Canto 07, Chapter 01, Text 12

SB 7.1.12

ya esa rajann api kala isita
 sattvam suranikam ivaidhayaty atah
tat-pratyanikan asuran sura-priyo
 rajas-tamaskan praminoty urusravah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
O King, this time factor enhances the sattva-guna. Thus although the Supreme Lord is the controller, He favors the demigods, who are mostly situated in sattva-guna. Then the demons, who are influenced by tamo-guna, are annihilated. The Supreme Lord induces the time factor to act in different ways, but He is never partial. Rather, His activities are glorious, and therefore He is called Urusrava.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
The Lord says in Bhagavad-gita (9.29), samo ’ham sarva-bhutesu na me dvesyo ’sti na priyah: “I envy no one, nor am I partial to anyone. I am equal to all.” The Supreme Personality of Godhead cannot be partial; He is always equal to everyone. Therefore when the demigods are favored and the demons killed, this is not His partiality but the influence of the time factor. A good example in this regard is that an electrician connects both a heater and a cooler to the same electrical energy. The cause of the heating and cooling is the electrician’s manipulation of the electrical energy according to his desire, but factually the electrician has nothing to do with causing heat or cold, nor with the enjoyment or suffering that results.
There have been many historical incidents in which the Lord killed a demon, but the demon attained a higher position by the mercy of the Lord. Putana is an example. Putana’s purpose was to kill Krsna. Aho baki yam stana-kala-kutam. She approached the house of Nanda Maharaja with the purpose of killing Krsna by smearing poison on her breast, yet when she was killed she attained the highest position, achieving the status of Krsna’s mother. Krsna is so kind and impartial that because he sucked Putana’s breast, He immediately accepted her as His mother. This superfluous activity of killing Putana did not diminish the Lord’s impartiality. He is suhrdam sarva-bhutanam, the friend of everyone. Therefore partiality cannot apply to the character of the Supreme Personality of Godhead, who always maintains His position as the supreme controller. The Lord killed Putana as an enemy, but because of His being the supreme controller, she attained an exalted position as His mother. Srila Madhva Muni therefore remarks, kale kala-visaye ’pisita; dehadi-karanatvat suranikam iva sthitam sattvam. Ordinarily a murderer is hanged, and in the Manu-samhita it is said that a king bestows mercy upon a murderer by killing him, thus saving him from various kinds of suffering. Because of his sinful activities, such a murderer is killed by the mercy of the king. Krsna, the supreme judge, deals with matters in a similar way because He is the supreme controller. The conclusion, therefore, is that the Lord is always impartial and always very kind to all living entities.
Srimad Bhagavatam Canto 07, Chapter 01, Text 11
Srimad Bhagavatam Canto 07, Chapter 01, Text 13