WSC Q.22: How did Christ, being the Son of God, become man?
Christ, the Son of God, became man, by taking to himself a true body, (Heb. 2:14,16, Heb. 10:5) and a reasonable soul, (Matt. 26:38) being conceived by the power of the Holy Ghost, in the womb of the Virgin Mary, and born of her, (Luke 1:27,31,35,42, Gal. 4:4) yet without sin. (Heb. 4:15, Heb. 7:26)
WLC Q.37: How did Christ, being the Son of God, become man?
Christ the Son of God became man, by taking to himself a true body, and a reasonable soul, (John 1:14, Matt. 26:38) being conceived by the power of the Holy Ghost in the womb of the Virgin Mary, of her substance, and born of her, (Luke 1:27,31,35,42, Gal. 4:4) yet without sin. (Heb. 4:15, Heb. 7:26)
WCF 8.2.
The Son of God, the second person in the Trinity, being very and eternal God, of one substance and equal with the Father, did, when the fulness of time was come, take upon Him man’s nature, (John 1:1, 14, 1 John 5:20, Phil. 2:6, Gal. 4:4) with all the essential properties, and common infirmities thereof, yet without sin; (Heb. 2:14, 16–17, Heb. 4:15) being conceived by the power of the Holy Ghost, in the womb of the virgin Mary, of her substance. (Luke 1:27, 31, 35, Gal. 4:4) So that two whole, perfect, and distinct natures, the Godhead and the manhood, were inseparably joined together in one person, without conversion, composition, or confusion. (Luke 1:35, Col. 2:9, Rom. 9:5, 1 Pet. 3:18, 1 Tim. 3:16) Which person is very God, and very man, yet one Christ, the only Mediator between God and man. (Rom. 1:3–4, 1 Tim. 2:5)