The Heidelberg Catechism, This Lord's Day week 18

Q49: What benefit do we receive from Christ's ascension into heaven?

A49: First, that He is our Advocate in the presence of His Father in heaven.[1] Second, that we have our flesh in heaven as a sure pledge, that He as the Head will also take us, His members, up to Himself.[2] Third, that He sends us His Spirit as an earnest,[3] by whose power we seek those things which are above, where Christ sits at the right hand of God, and not things on the earth.[4]
1. I John 2:1; Rom. 8:342. John 14:2; 20:17; Eph. 2:63. John 14:16; Acts 2:33; II Cor. 5:54. Col. 3:1; John 14:3; Heb. 9:24

Q50: Why is it added: "And sitteth at the right hand of God"?

A50: Because Christ ascended into heaven for this end, that He might there appear as the Head of His Church,[1] by whom the Father governs all things.[2]
1. Eph. 1:20-23; Col. 1:182. John 5:22; I Peter 3:22; Psa. 110:1