The basis of the Christian faith is the idea that we were created by a God whose only desire for us is to be happy with Him forever in a bond of unifying love. As the three Persons of the Holy Trinity exist in perfect unity through Their infinite, eternal love for each Other, so God wants us to be a part of that Union. The Holy Trinity, living in a bond of love, is best described analogously by family. Our entry into that Family is like an adoption, and we take on the nature of the family, the Divine Nature (see 2 Pet 1:4). We become children of God with a real, kinship bond between Him and us.
In ancient Semitic culture, the establishment of kinship bonds between persons occurred via a covenant. The method of a covenant was to swear an oath to God that the persons would maintain their relationship until death; this ritual oath included a sharing of food and drink (for example, see Gen 26:23-33, Ex 24:1-11, Mk 14:22-24). You may notice that we still apply this ancient method in matrimony, where two people unrelated by blood form a very real kinship bond and create a new family (we exchange vows - swear the oath - then we have a festive reception). The great God, who always meets us where we are, adopted this covenant method to describe Himself to the Israelites. The Old Testament is filled with covenantal language, matrimonial language and the language of family to describe our relationship with God.
As we read Scripture, we also notice a number associated with the covenant: seven. It’s always there, lurking nearby in every covenant narrative. For example, among the above mentioned examples, read on from Ex 24:1-11 a few more verses to verse 16:
The glory of the LORD settled on Mount Sinai, and the cloud covered it six days; and on the seventh day he called to Moses out of the cloud. (Ex 24:16)
Likewise in Gen 21:28 above, Abraham sets apart seven ewe lambs. The number seven is so linked to the notion of a covenant oath, that in Hebrew the same word is used for both oath and seven: sheva. Why seven?
One idea is that it refers to the seven days of creation. On the sixth day, God creates animals, including the human. But God applies family language when creating humans; He says,
“Let us make man in our own image, after our own likeness…” 27 So God created man in his own image, in the image of God he created him, male and female he created them. (Gen 1:26-27)
This phrase including image and likeness is family language, referring to parent & child; as an example see Gen 5:3. For some pre-Christian rabbis, the meaning here is that God swore a covenant oath with Adam & Eve, the oath being this family formula; the seventh day immediately follows. Thus, seven is the number of the covenant oath. Furthermore, on the sixth day God created the animals, which is all we are without God's covenant; therefore, the number six represents “not-the-covenant.” We can then see the number six occur in Scripture when referring to particularly un-covenantal persons or relationships (for example Dan 3:1, 1 Kgs 10:14 & 1 Kgs 10:18-20). Thus, seven hearkens back to the original covenant between God and humanity, with its sign of the seventh day and the memorial sabbath.
Another idea, which involves many different scriptural references, concerns the fact that God is a Trinity. Also, humans are a microcosmic trinity in that we are composed of a body, a soul and the Spirit of God (see 1 Thes 5:23, 1 Jn 5:8 vulgate). Thus God is three and humans are three. So, when God and a human enter into a union, we get 3 + 3 = 6, right? No, this is not a semitic way of thinking; we need to think geometrically, rather than arithmetically. Consider a triangle with apex pointing upward; this represents the Triune God. Consider another triangle with apex downward, this represents the triune human. Now overlay the two triangles on each other; the result is the Magen David – the Star of David, which is well recognized as the primary symbol of Judaism. Again, it may seem to us a six-pointed star, but consider that it is also a set of seven shapes (draw it and see); the seven geometric shapes point to a new, seventh thing that results when combining the two trinities: the God-man. Thus, the number directly describes the union of God and man.
A final comment on the number seven: As noted, Hebrew uses the same word – sheva – for both seven and oath; and a covenant requires the swearing of a covenant oath. In Latin, the word for oath is sacramentum. This is, of course, the root of the word sacrament, easily recognized by Catholics as our seven-fold means of grace. And this introduces a world of additional covenantal imagery: water, wine, bread, eating, drinking, blood, sacrifice, lambs, altar, offerings, priesthood, etc. Re-read the above three OT examples in the above 2nd paragraph with this imagery in mind. Try it now.
Likewise, reconsider our sacramental faith in terms of family, matrimony and covenant. God is our Father. The Church is His bride. We are the children of God. We receive His Life – called grace – through the seven oaths (sacraments). The family comes together every seventh day for a festive meal, where we invoke our family name (“In the name of the Father, the Son and the Holy Spirit” – the Divine Family).