न बुद्धिभेदं जनयेदज्ञानां कर्मसङ्गिनाम्।जोषयेत्सर्वकर्माणि विद्वान् युक्तः समाचरन्॥
na buddhi-bhedaṃ janayed ajñānāṃ karma-saṅgināmjoṣayet sarva-karmāṇi vidvān yuktaḥ samācaran
Word by word
The verse says
Do not unsettle the minds of people who are attached to what they do. Let the one who knows keep working, well, and draw them in that way.
In plain words
A rule about teaching, and it is a restraining one.
Buddhi-bheda — splitting someone's understanding. Do not do it to a person who is working happily for results.
Instead: joṣayet — make it attractive. By doing the thing yourself, properly.
Where you've felt this · in friendship
A friend is deep in something that is working for them and you can see its limits. Saying so would take the thing away and put nothing in its place. You keep doing your own thing, well, and stay available.
Going deeper
This is the Gita being careful about what a half-understood teaching does to someone.
The risk is specific. A person acts for results, and the results motivate them, and the work gets done. Tell them the results do not matter, and if they only half-accept it, you have removed the motor without installing the replacement. What is left is neither engaged work nor free work. It is just less work.
Buddhi-bheda names exactly that — a split in the understanding, where the old reason has been discredited and the new one has not landed.
So the instruction is not to withhold the truth. It is to transmit it by demonstration rather than by argument, which is verse 21 turned into a teaching method.
There is a restraint here worth admiring. A text confident of its own teaching is telling its readers not to go around correcting people. The Gita is unusual among scriptures in that.
And the mechanism is patient. You do the thing well. People are drawn. Nobody has been argued out of anything.