Lyric discussion by mandagemini 

Cover art for Oye Como Va lyrics by Santana

I think the pa' might stand for para ("for").

@mandagemini yes I agree that “pa” is for para. Listen more closely and I think you will hear the r. It’s “par’ gosar” rather than pa’ gosar. The vowel elides but not the consonant.

@mandagemini \r\nIt\'s "la boca floja", slurred, slangy speech, just like in Rockn\'Roll