“[…] Speaking the truth, let us by love grow up in all things into him who is the head, Christ.”
~Ephesians 4:15

How can I “grow up” by love, becoming a more spiritually mature Christian?
Mature Christians look for ways to promote unity in the congregation. (John 17:21,22; Eph. 4:2-4,13,16)
Instead of holding grudges, mature Christians consistently overlook the flaws of their brothers and sisters.
They view others with mercy and compassion. (Eph. 4:25,26; 31,32)
In the above passage, the Greek phrase “alitheiontes” literally means to maintain the truth.
This implies upholding Bible principles even when no one is watching. (Eph. 6:6)
But to be a mature Christian, it is not enough to obey systematically.
I have to be motivated by love.