How to know who is good from that which is not?

30 “He who is not with me is against me, and he who doesn’t gather with me, scatters.

- G.S.Notes

31 Therefore I tell you, every sin and blasphemy will be forgiven men, but the blasphemy against the Spirit will not be forgiven men. 32 Whoever speaks a word against the Son of Man, it will be forgiven him; but whoever speaks against the Holy Spirit, it will not be forgiven him, either in this age, or in that which is to come.

33 “Either make the tree good and its fruit good, or make the tree corrupt and its fruit corrupt; for the tree is known by its fruit.

34 You offspring of vipers, how can you, being evil, speak good things? For out of the abundance of the heart, the mouth speaks.

Matthew 12:30-34 (WEB)