The Greek phrase ei tis combines the conditional particle ei (if) with the indefinite pronoun tis (anyone, someone). This construction introduces conditions that are universal in application — 'if anyone' means every person who fulfills the condition. It is one of the most flexible and theologically loaded constructions in Greek.
Ei tis appears in some of Christianity's most significant statements of both invitation and warning. 'If anyone is thirsty, let him come to me and drink' (John 7:37). 'If anyone wishes to come after me, let him deny himself' (Matt 16:24). 'If anyone builds on this foundation using gold, silver, costly stones...' (1 Cor 3:12). The construction is both universal (open to all) and demanding (each person must choose). It captures the gospel's simultaneous offer to everyone and personal demand on each individual.