One verse

Srimad Bhagavatam 4.1.59

4.1.59

ताविमौ वै भगवतो हरेरंशाविहागतौ । भारव्ययाय च भुव: कृष्णौ यदुकुरूद्वहौ ॥ ५९ ॥

tav imau vai bhagavato harer amsav ihagatau bhara-vyayaya ca bhuvah krsnau yadu-kurudvahau

tau
both
imau
these
vai
certainly
bhagavatah
of the Supreme Personality of Godhead
hareh
of Hari
amsau
part and parcel expansion
iha
here (in this universe)
agatau
has appeared
bhara-vyayaya
for mitigation of the burden
ca
and
bhuvah
of the world
krsnau
the two Krsnas (Krsna and Arjuna)
yadu-kuru-udvahau
who are the best of the Yadu and Kuru dynasties respectively.

That Nara-Narayana Rsi, who is a partial expansion of Krsna, has now appeared in the dynasties of Yadu and Kuru, in the forms of Krsna and Arjuna respectively, to mitigate the burden of the world.