Of this man’s seed (toutou apo tou spermatos). Emphatic position of toutou. Of this one from the (his) seed.
According to promise (kat' epaggelian). This phrase in Gal 3:29; 2Ti 1:1. See the promise in 2Sa 7:2; Psa 132:11; Isa 11:1, Isa 11:10; Jer 23:5.; Zec 3:8. In Zec 3:8 the verb agō is used of the sending of the Messiah as here.
A Saviour Jesus (Sōtēra Iēsoun). Jesus is in apposition with Saviour (accusative case) and comes at the end of the sentence in contrast with “this man” (David) at the beginning. Paul goes no further than David because he suggests to him Jesus, descendant in the flesh from David. By “Israel” here Paul means the Jewish people, though he will later enlarge this promise to include the spiritual Israel both Gentile and Jew (Rom 9:6.).