Before assuming the responsibilities involved in marriage, young men and young women should have such an experience in practical life as will prepare them for its duties and its burdens. Early marriages are not to be encouraged. A relation so important as marriage and so far-reaching in its results should not be entered upon hastily, without sufficient preparation, and before the mental and physical powers are well developed. MH 358.1 The parties may not have worldly wealth, but they should have the far greater blessing of health. And in most cases there should not be a great disparity in age. A neglect of this rule may result in seriously impairing the health of the younger. And often the children are robbed of physical and mental strength. They cannot receive from an aged parent the care and companionship which their young lives demand, and they may be deprived by death of the father or the mother at the very time when love and guidance are most needed. MH 358.2 It is only in Christ …
"Prepare thy work without, and make it fit for thyself in the field; and afterwards build thine house."
Both passages emphasize the importance of preparation before building a house/entering marriage. Proverbs 24:27 advises preparing the field before building a house, while EGW advises practical life experience and maturity before marriage. The underlying principle of preparation is the same.
"Love is a precious gift, which we receive from Jesus. Pure and holy affection is not a feeling, but a principle. Those who are actuated by true love are neither unreasonable nor blind. Taught by the Holy Spirit, they love God supremely, and their neighbor as themselves. MH 358.4"
"Jesus said unto him, Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second is like unto it, Thou shalt love thy neighbour as thyself."
EGW directly alludes to the command to love God and neighbor as oneself, which is the core message of Matthew 22:37-39. She uses this as a foundation for her discussion of love as a principle.
"Beloved, let us love one another: for love is of God; and every one that loveth is born of God, and knoweth God."
Both passages discuss the nature and source of love. EGW expands on the idea that love is a principle, not just a feeling, and that it comes from God, echoing the sentiment in 1 John 4:7.