I prayed in a chasidic shul in europe. They did not say tachnun in sharis of friday and sunday.
I asked them what the reason is and they answered me that in the days close to shabbes tachnun should not be recited.
Is there a halachic source (makor) for this?
The closest answer i could find was this: Special occasions where various Chassidim don't say Tachanun
It just speaks on friday and there is a source of a siddur but not a halachic sefer.