CONFESS: IN THE OLD TESTAMENT
Compare what David, a believer, states in Psalm 32:5:
"I [David] acknowledged my sin to Thee,
And my iniquity did not hide;
I said, 'I will confess my transgressions to the LORD'
And Thou didst forgive the guilt of my sin."
Note that old testament saints were saved unto eternal life in the same faith alone in Christ (the Messiah Savior) alone way except that they looked forward to the time of the cross, (ref. Ro 4:1; Jn 3:16; Heb 11:4, 13); whereas church age believers look back in time, (Eph 1:3-2:9).
Fellowship with God for old testament believers came as a result of confession and practice of various acts such as stipulated under Mosaic Law, (cp Lev 4:3, 5:5; 5:15-19; Ex 30:19-21, 40:11-12, 30-31; Pr 28:13; Ps 32:5).
[Compare Lev 5:5-6]:
(v. 5) "When anyone is guilty in any of these ways [vv. 1-4], he must confess in what way he has sinned
(v. 6) and, as a penalty for the sin he has committed, he must bring to the LORD a female lamb or goat from the flock as a sin offering; and the priest shall make atonement for him for his sin."
The sacrifice of a goat or a lamb under certain Mosaic Law provisions was meant to be a picture of an individual's acknowledgment to God of certain sins committed which then results in God's forgiveness of those 'confessed' sins:
(v. 27) "Now if anyone of the common people sins unintentionally in doing any of the things which the LORD has commanded not to be done, and becomes guilty.
[i.e., becomes aware of his sin]
(v. 28) if his sin, which he has committed is made known to him, then he shall bring for his offering a goat, a female without defect, for his sin which he has committed.
(v. 29) And he shall lay his hand on the head of the sin offering, and slay the sin offering at the place of the burnt offering.
(v. 30) And the priest shall take some of its blood with his finger and put it on the horns of the altar of burnt offering; and all the rest of its blood he shall pour out at the base of the altar.
(v. 31) Then he shall remove all its fat, just as the fat was removed from the sacrifice of peace offerings; and the priest shall offer it up in smoke on the altar for a soothing aroma to the LORD. thus the priest shall offer it up in smoke on the altar for a soothing aroma to the LORD. Thus the priest shall make atonement for him, and he shall be forgiven.
(v. 32) But if he brings a lamb as his offering for a sin offering, he shall bring it, a female without defect.
(v. 33) And he shall lay his hand on the head of the sin offering, and slay it for a sin offering in the place where they slay the burnt offering.
(v. 34) And the priest is to take some of the blood of the sin offering with his finger and put it on the horns of the altar of burnt offering; and all the rest of its blood he shall pour out at the base of the altar.
(v. 35) Then he shall remove all its fat, just as the fat of the lamb is removed from the sacrifice of the peace offerings, and the priest shall offer them up in smoke on the altar, on the offerings by fire to the LORD. Thus the priest shall make atonement for him in regard to his sin which he has committed, and he shall be forgiven."
[Compare Pr 28:13]:
"He who conceals his transgressions will not prosper,
But he who confesses and forsakes them will find compassion."