Meaning
Supreme God Krishna spoke
However, those devoted followers who adhere to the principles of religion I have outlined above are extremely dear to Me. (12:20)
Sanskrit
श्रीभगवान् उवाच
ये तु धर्म्यामृतमिदं यथोक्तं पर्युपासते ।
श्रद्दधाना मत्परमा भक्तास्तेऽतीव मे प्रियाः॥
Word-by-word
ये तु धर्म-अमृतम् इदम् यथा उक्तम् परि-उपासते,
श्रद्दधानाः मत्-परमाः भक्ताः, ते अतीव मे प्रियाः।
Commentary
In verse 12:13 to 12:19, God repeatedly refers to individuals as "dear to Me." Towards the end, in verse 12:20, He emphasizes that those who actively apply these teachings in their lives are "extremely" dear to Him.
Who else, besides those who are dear or extremely dear to God, will attain happiness here and hereafter, and ultimately Liberation or Nirvāna.