Here is Bede says in his commentary
(6:5) Then the angel of the Lord said to him, ‘Disembowel this fish and lay aside for yourself its heart, gall-bladder and liver.’ The Lord disemboweled the fish when he plainly revealed the devil’s wickedness to the saints and cut out the secrets, as it were, of his snares. He set aside for himself his heart because he wanted to point out to the saints, from Scripture, the devil’s cunning, about which it says, Now the serpent was more cunning than all the creatures of the earth. (Gen. 3:1) Of that heart Paul also said, For we are not ignorant of its designs. (2 Cor. 2:11) He set aside even his gall-bladder because, on account of his zeal for caution, he wanted it to be written and remembered with how much malicious frenzy the devil rages against humankind. He also set aside the liver because he deigned to show us through teachers of truth the seasoned male violence of Satan’s ruminations against us. For they say that the liver’s heat and secret strength boil down foods that have been swallowed so that they can be digested. For when by careful meditation we truly inquire about in which those things that we determine to do should be completed, we boil them down, just as we, using the liver’s heat, boil down foods taken into the stomach.
(6:6) Tobia roasted the fish’s flesh, and they took it with them on their way. The rest they salted, as much as they needed. The part of the fish that they took with them represents those who were transferred from being the devil’s members to Christ’s, that is, those who were converted from unbelief to faith. By contrast, the part that they threw out represents those who have heard God’s word yet would rather dwell among their deceiver’s dead and rotten members than return to the company of the Savior. He cooked the fish’s flesh in those whom he found to be fleshly-minded, but by the fire of his love he rendered them spiritual and strong. And so the Holy Spirit descended on the apostles in a vision of fire. The rest, it says, they salted. This pertains especially to the teachers to whom it is said, You are the salt of the earth. (Mt. 5:13) Now they (that is Tobia and the angel) salted because the same mediator between God and humans both humanly taught the apostles by his speech and divinity granted them the salt of wisdom in their hearts