προς preposition
pros  pros: a preposition of direction; forward to, i.e. toward
ον relative pronoun - accusative singular masculine
hos  hos: the relatively (sometimes demonstrative) pronoun, who, which, what, that -- one, (an-, the) other, some, that, what, which, who(-m, -se), etc.
ελαληθη verb - aorist passive indicative - third person singular
laleo  lal-eh'-o: to talk, i.e. utter words -- preach, say, speak (after), talk, tell, utter.
οτι conjunction
hoti  hot'-ee: demonstrative, that (sometimes redundant); causative, because -- as concerning that, as though, because (that), for (that), how (that), (in) that, though, why.
εν preposition
en  en: in, at, (up-)on, by, etc.
ισαακ proper noun
Isaak  ee-sah-ak': Isaac (i.e. Jitschak), the son of Abraham -- Isaac.
κληθησεται verb - future passive indicative - third person singular
kaleo  kal-eh'-o: to call (properly, aloud, but used in a variety of applications, directly or otherwise) -- bid, call (forth), (whose, whose sur-)name (was (called).
σοι personal pronoun - second person dative singular
soi  soy: to thee -- thee, thine own, thou, thy.
σπερμα noun - nominative singular neuter
sperma  sper'-mah: something sown, i.e. seed (including the male sperm); by implication, offspring; specially, a remnant (figuratively, as if kept over for planting) -- issue, seed.