What is God the Father's gender?

Thanks for your question. God the Father is a spiritual Being (John 4:24; cf. Luke 24:39), not a sexual one. God the Father does not have a physical body and He has absolutely no physical male or female features. He doesn't have an X or Y chromosome. Male and female are biological terms, but God the Father is not a biological Being. God is a spirit, so He doesn't have a gender. The same goes for the Holy Spirit as well.

This said, God the Father has chosen to reveal Himself to humanity using mostly a masculine imagery and pronouns in Holy Scripture, which He Himself inspired (2 Tim. 3:16-17; 2 Pet. 1:20-21). Throughout the Bible, we observe references to God as King (Psa. 24:10; 47:2; Isa. 44:6; 1 Tim. 1:17, etc.), Father (Deut. 32:6; Mal. 2:10; Luke 11:2; 1 Cor. 8:6, etc.), and even a Husband (Isa. 54:5; Hos. 2:2, 16, 19.).

Though God who is a spirit can not have a genuine male or female gender, throughout the Bible, the pronouns used of God the Father are grammatically masculine (cf. Gen. 1:26-27; Deut. 4:35; 1 Kings 18:39; Psa. 95:7; 100:3; 138:8; Isa. 40:11; 64:8, et.al.); note that Biblical Hebrew has no gender-neutral pronouns. Even in Greek, Theos meaning God, is referred to with a masculine gender (note the masculine "os" ending on Theos); e.g. the Hebrew words for God, Yahweh, Elohim, Adonai, and another Greek term for God, Kurios are all in the masculine gender as well. The greatest revelation of God the Father to us is His Son, the Lord Jesus Christ (Heb. 1:2), who is the second and last Adam (1 Cor. 15:45, 47); compare the fact that even though God made mankind in His own image - male and female he created them (Gen. 1:27) - He blessed them and called their name Adam - the first male (Gen. 5:2). Jesus came to save His people from both genders (Luke 19:10). While the Hebrew word for "spirit" (ruach) is feminine in Genesis 1:2, the Holy Spirit is referred to in the masculine throughout the New Testament, although the word for "spirit" (pneuma) is gender-neutral. Besides the Hebrew word for "spirit" (ruach) is combined with the masculine Elohim in Hebrew for the Holy Spirit. But, as already stated above, the gender of a word in Hebrew or Greek has nothing to do with gender identity of God the Father Himself, as He has none because He is a spirit (John 4:24).

However, in Scripture, we occasionally see both God's personage, character, and actions described by feminine imagery (Num. 11:12; Deut. 32:18; Ruth 2:12; Job 38:8, 28-29; Psa. 17:8; 22:9-10; 90:2; 91:4; 123:2; 131:2-3; Prov. 8:1, 22-25; Isa. 31:5; 42:13-14; 45:10; 46:3; 49:15; 63:15; 66:7-13; Hos. 13:8; Matt. 23:37; Luke 13:34; 15:8-10; John 3:3-8; 1 Pet. 2:2-3). This is fitting as things like compassion and caring fit a female genre more than a male. But none of these passages necessitate or mean that we should ever refer to God the Father as a female; God the Mother, et. al.

Why?

First, it is not uncommon in Scripture, and other writings, to observe feminine imagery applied to the male gender (2 Sam. 17:8; Isa. 60:16). Even the circumcised (Phil. 3:5) Apostle Paul used it of himself (Gal. 4:19; 1 Thess. 2:7). God delights in the proper use of symbolism, poetry, metaphor, and imagery as genres, even to describe Himself at times.

Second, just because female imagery is occasionally used to describe God, this does not make Him intrinsically feminine any more than Greek words which take the feminine article such as aletheia, meaning truth, or hamartia, meaning sin, mean they are actually feminine.

Third, the tiles of God the Father referred to in Scripture are typically applied to males, not females (i.e. judge, ruler, savior). Items such as fortresses, rocks, and shields and persons such as shepherds and warriors are also typically associated with males in that era, not females.

Fourth, while God the Father is the God of all His covenant people - both male and female - He regularly refers to Himself as the God of Abraham, the God of Isaac, and the God of Jacob (Gen. 50:24; Exod. 3:6, 15, 16; 4:5; 1 Kings 18:36; Matt. 22:32; Mark 12:26; Luke 20:37; Acts 7:32), not as the God of Sarah, Rebecca, and Rachel. While this is not in any way meant to demean women, it reveals that God identifies with the male covenant heads of families. Thus, though God the Father has no gender, it would be proper that God also, as the Head of the Eternal Covenant (Isa. 55:3; Jer. 32:40; Ezek. 16:60; 37:26: Heb. 13:20), to identify and associate Himself as a covenant male figure, not a female.

So, even though God the Father is a spirit and doesn't have a gender, it is still proper to refer to God as being a He. Moreover, though God the Father transcends gender, He has chosen to consistently refer to Himself as a He. God is described in mostly male terms because that best describes how God relates to His creation. So, while understanding the fuller reality, we should follow God the Father's lead and therefore refer to Him as a He, not a she.

As to The Shack, by William Paul Young, it is an unbiblical book/movie. It contains numerous theological errors, among them being: (1) Mack meets the divine trinity as Papa, a woman, Jesus as a Jewish carpenter, and Sarayu, another woman, who is supposedly the Holy Spirit; (2) Papa, allegedly God the Father with wrist scars, supposedly suffered with Jesus on the Cross; (3); the jesus of The Shack says to Mack that he is the "best way" any person can relate to Papa, not the "only way" (cf. John 14:6); (4) it teaches universal redemption; (5) the god of The Shack seems nonchalant about holiness; (6) it marginalizes repentance; (7) teaches there is no such a thing as eternal torment in an everlasting Hell; and (8) it utterly disrespects the authority of the Word of God, etc. IMO, The Shack is a complete work of fiction entirely void of the inerrant truth of Scripture. IMO, it's good for only one thing, starting a fire in the fire place.