This is a verse of the 11th chapter of Bhagavad Gita. It tells the 5 things we have to do daily. Srila Prabhupada called this verse as the essence of the Bhagavad Gita. Anyone who wants to reach the Lord in the spritual sky MUST FOLLOW these 5 things. Then we can certainly go back to Lord Krishna.
The verse is as follows:
mat-karma-krn mat-paramo
mad-bhaktah sanga-varjitah
nirvairah sarva-bhutesu
yah sa mam eti pandava
Translation: My dear Arjuna, he who engages in My pure devotional service, free from the contaminations of fruitive activities and mental speculation, he who works for Me, who makes Me the supreme goal of life, and he who is friendly to every living he certtainly comes to Me.
So from this verse we can understand that engaging in the service of Krishna, being free from material contaminations, we must work for him, we must make him the biggest goal in his life, and we must be friendly to all, the we can go back to him.