This isn't exactly a slang phrase, but a common saying in Spanish. It means 'it's good to check the ID from time to time', implying that it's wise to reevaluate or reassess situations or people now and then.
Examples
- Spanish: No te fíes ciegamente de las personas, es bueno mirar el carné de vez en cuando.
- English: Don't blindly trust people, it's good to check the ID from time to time.