Nowhere in his epistles or in the Revelation does the apostle use the term “Holy Spirit,” although he clearly speaks of the third person of the Godhead.

 Literally, “and in this,” referring forward to the gift of the Spirit mentioned at the end of the verse. The presence of the Spirit in the Christian’s life is a proof that God is dwelling in him, for it is through the Spirit that God abides in a man (Rom. 8:9, 11, 14-16; 1 Cor. 3:16). An almost identical thought is expressed in 1 John 4:13.

 The indwelling is always mutual (see John 15:4, 5). He who wishes to dwell with God may be sure that God has ever wanted to dwell with him. But man must show he is in harmony with the Lord by willingly keeping His commandments.

 He who keeps the commandments of God has the privilege of making his home with God. Using a different figure, Amos asks, “Can two walk together, except they be agreed?” (Amos 3:3). No one can be at home with God while living contrary to His expressed will, but he who is willing to do the will of God can permanently make his home with the Almighty.

 That is, God’s commandments (see on ch. 2:3). If we keep God’s commandments, we have confidence toward God, we receive whatsoever we may ask (ch. 3:22) and, as a further consequence, we have close fellowship with God.

 Or, “whom” (see on Rom. 8:16).

 Rather, “gave,” since John is here referring to the time when the believers first received the Holy Spirit. That the Father gives the Spirit is made clear in John 14:16, although the Son cooperates in sending the third person of the heavenly trio (cf. John 16:7).