Chill is an interesting word choice because it's an English loanword directly incorporated into the Spanish lyrics. While it literally means "cold," in this context, it's used colloquially to mean "calm" or "relaxed."
In the song, the line "En la prueba estoy chill" (In the trial, I am chill) conveys a sense of peace and confidence even amidst challenges, highlighting a modern, informal expression within a spiritual song.
Montesanto open by borrowing a line straight out of Psalm 121: "Alzaré mis ojos a los montes" (I will lift my eyes to the mountains). That is a question about where help comes from, and the band take a full minute answering it before the beat properly arrives.
Then the song picks its hero. "Haré así, como David" (I will do it this way, like David), meaning David: the king who fought a giant with a sling and later danced in the street until his wife was embarrassed. Montesanto turn that into a rule for their own fights, "Mi alabanza, será mi arma" (My praise will be my weapon). Jairon High takes the second half and drops the register completely, from psalm Spanish into street Spanish. "En la prueba estoy chill" (In the trial I stay chill) is basically a shrug. "Por causa de Él, me haré más vil" (Because of Him, I will make myself even more undignified) is lifted almost word for word from 2 Samuel 6:22, where David answers that embarrassment by promising to go lower still. The best line is the one that closes it, "Hay fiesta en el desierto" (There is a party in the desert), a party thrown in the one place where nothing grows.